A multi-platform Atari 2600 VCS emulator

Release 6.2.1

User's Guide


February 1999 - June 2020
The Stella Team
Stella Homepage

A Brief History of the Atari 2600

In the early 1970's, video arcade games gained commercial success for the first time. The American public was introduced to Pong, Tank, and other interactive video games which populated amusement parks, bars, and arcades. The games were successful enough to create interest for home versions, so in 1975 Atari released Home Pong and it was a smash hit. Other companies such as Magnavox and Coleco followed suit and released their own dedicated console games. Then in 1976, Fairchild Camera and Instrument introduced the Channel F system, the first cartridge based home video game system. The industry recognized that cartridge systems were the future of video gaming, and began development in that direction. In January 1977, RCA released the Studio II, another cartridge based system, although it only projected in black and white and seemed to be focused on educational titles. Then, in October 1977, Atari released the Atari VCS (Video Computer System) with an initial offering of nine games. This system, later renamed the Atari 2600, took the industry by storm and dominated the marketplace for years to come.

Because of oversupply, the Christmas season of 1977 was very rough on the video game industry, and the Atari 2600 was the only system that managed to emerge unscathed. Atari enjoyed strong sales in 1978 and a fantastic holiday season, as Atari released more games such as Outlaw, Spacewar, and Breakout. Internally however, Atari was at odds. Nolan Bushnell, the inventor of pong and founder of Atari, wound up leaving the company and purchased Pizza Time Theater, which later became the successful Chuck E. Cheese! In 1979 Atari continued their trend and released 12 more games which met with continued success. However, Atari was now facing some stiffer competition from the Mattel Intellivision and the Magnavox Odyssey2.

Atari needed a mega-hit in 1980 in order to squash the competition, and they found it in the home version of a game from Japan called Space Invaders. It was so popular that people were buying the Atari 2600 just so they could play Space Invaders at home. Following that, Atari released Adventure, which was the first video game to contain an Easter Egg - placing an object in a certain area revealed the programmer's name, Warren Robinett. 1980 was important for another reason - the creation of the first ever third party software producer, Activision. The company was formed by four Atari employees who were unsatisfied with the working conditions at the company. They released four games initially: Dragster, Fishing Derby, Checkers and Boxing. The games were very well received by the public, and revealed that the Atari 2600 was capable of better games than Atari themselves had been producing. Atari tried to prevent Activision from selling games, but they failed and Activision grossed $70 million that year.

By 1981, the video game industry was basically a horse race between the 2600 and the Intellivision. While the Intellivision was technologically superior in some respects, the 2600 continued to lead in sales. Atari released the home version of Asteroids, which was a huge success. Inspired by the success of Activision, another software development group called Imagic was formed. They would not release any games until 1982 however. Another company, Games by Apollo, was formed in Texas and released several games that year.

Coleco entered the market in 1982 with the release of the graphically superior Colecovision. To combat this new system, Atari produced the 5200, a technologically comparable system. The 2600 dropped $100 in price in order to remain competitive. Then a company called Arcadia released a peripheral called the Supercharger which played games in an audio cassette medium. This allowed for multiple loads and expanded the 2600's capabilities.

Atari released Pac-Man and E.T. that year, two incredibly hyped games which were critical flops. Although Pac-Man sold many copies, it was considered to be a poor translation of the arcade hit. However, there were many fantastic games produced for the 2600 during this period, and it was still selling strong.

Ever since the inception of Activision, Atari had been fighting to keep third parties from producing cartridges which they felt were stealing profits from them. Finally the issue was settled when Atari agreed to allow third party manufacturing in exchange for a royalty. Suddenly software companies began popping up all over, and 1982 saw releases from companies like Venturevision, Spectravision, Telesys, CBS, 20th Century Fox, US Games, M Network, Tigervision, Data Age, Imagic and Coleco. There was even a company that released a line of X-Rated games for the 2600 called Mystique. The year was financially successful for Atari, however there seemed to be a glut of software. Although there were many quality titles still produced, there was an increasing number of rushed games as manufacturers attempted to cash in on the craze.

More companies jumped on the band wagon in 1983. Zimag, Ultravision, Amiga, and others were also producing games and peripherals. It seemed as if there was just too much product to meet the demand, and as it turned out there was. By the end of the year, companies began folding. US Games, Data Age, Games by Apollo, Telesys and others all closed their doors from poor sales. A video game crash was occurring, and all companies were taking it on the chin.

1984 was a much more subdued year for the Atari 2600, and the price of the system had now dropped to $40-$50. Many were saying that the video game industry was dead. However, Atari surprised everyone by announcing the release of the 7800, and also promising more 2600 games with improved graphics and sound. Unfortunately, neither of these things happened in 1984 because Atari sold their home video game division to Jack Tramiel who believed that home computers would replace video game systems. No further mention of the 2600 or 7800 was made that year, and it appeared that they might be dead.

1985 was another very quiet year for Atari and video games in general, and only a few games were released for the 2600. Activision produced Cosmic Commuter and Ghostbusters, but with little fanfare or marketing, these games did not sell well. However, because of the huge game library and cheap price, Atari still sold over a million 2600 consoles in 1985.

There were very few plans for home video game systems by any company in 1986, since the market appeared to be dead. Then, to most people's surprise, Nintendo brought the NES to America and it was a smash hit, proving that video games still had a place in the US. Atari decided that maybe it would be a good idea to release the 7800 units it had in storage, and produce some more 2600 games. The 7800 was released with only 3 games initially available, although it was compatible with the 2600 library. They also redesigned the 2600 as the 2600 Jr., a machine with the same abilities, but a new look and marketing campaign. It was sold for less than $50.

Video games were once again selling phenomenally in 1987. Atari released several new titles, including Jr. Pac-Man, and also licensed a number of games from other companies such as Donkey Kong and Q*Bert. These new titles sold for $10-$15. Interestingly, a number of titles began appearing again from third part companies such as Epyx, Froggo, and Exus. It seemed that the 2600 was not dead yet!

In 1988, Atari rehired Nolan Bushnell and announced a number of new titles, including Secret Quest, a game written by Mr. Bushnell himself. Atari continued to manufacture these games even until 1989. However, it was apparent that the 2600, after its introduction over a decade ago, was finally at the end of its run. Although it was still produced and marketed outside of the US, the Atari 2600 finished its run in America. No other console has had such a long history or sold as many systems in the U.S.

Today, the 2600 still has a large number of fans who remember the countless games played over the years, and the years to come. There are even games being produced by hobbyists, some of them quite professionally, being released on newly burnt cartridges with labels and manuals. And the recent trend in retrogaming has brought many more video game fans to rediscover the 2600, and it continues to live on 22 years after its release!

Alexander Bilstein
February 1999


Stella is a freely distributed multi-platform Atari 2600 VCS emulator; originally developed for Linux by Bradford W. Mott, it is now maintained by Stephen Anthony. Stella allows you to enjoy all of your favorite 2600 games once again by emulating the 2600's hardware with software. Stella is written in C++, which allows it to be ported to other operating systems and architectures. Since its original release Stella has been ported to AcornOS, AmigaOS, DOS, FreeBSD, Linux, MacOS, OpenStep, OS/2, Unix, and Windows, as well as consoles such as Sega Dreamcast, GP2X, Nintendo DS and Playstation Portable (among others).


Getting Started


The following sections outline the basic system requirements for running Stella under various operating systems.

General (required for all versions of Stella)


The Linux version of Stella is designed to work on a Linux Workstation with the following:


The Mac version of Stella is designed to work on an Apple Macintosh with the following:


The Windows version of Stella is designed to work on Windows Vista/7/8/10 with the following:


Stella is extremely portable, and in its lifetime has been ported to almost every platform where the SDL library exists. It is 32/64-bit and endian clean in Linux/Unix, macOS and Windows. The Stella Team is interested in hearing about any problems you may encounter with diverse operating systems and CPU types.


Stella is distributed in both source and binary form. In general, you should always download and install the appropriate binary version. Compiling from source is only recommended for developers, or if the binary version doesn't work for some reason. Once you have a Stella distribution you should follow the instructions for your operating system given below.




Locating Game Images (aka ROMs)


Most games for the Atari 2600 came on cartridges. A cartridge usually consists of a single Read Only Memory (ROM) chip which contains the data and code for the game. Plugging a cartridge into the Atari 2600 allows the 2600's microprocessor to access the program stored on the cartridge.

In a similar way you must "plug" a copy of a cartridge into Stella when you want to play it. Having a ROM image/BIN file of the cartridge allows you to do this. A ROM image is a file, which contains the actual data and code read from the cartridge. There are several ways to obtain a ROM image of a cartridge:

WARNING: It may be illegal to use ROM images of games that you do not actually own since these games may still be copyrighted.

Supercharger Cassettes

Supercharger games were not stored on cartridges instead they were stored on cassette tapes. The Supercharger, which plugged into the Atari 2600's cartridge slot, loaded games into its 6K of Random Access Memory (RAM) using a standard audio cassette player. The Supercharger also supported multi-loading, which allowed games to be broken into several segments and loaded at different times. This was useful for large games which had distinct parts such as role playing games.

Most of the available Supercharger ROM images are stored in 8448 bytes files. However, ROM images of multi-load games are sometimes stored in a set of 8448 byte files. The names of these files have a two character sequence number in them which indicates what load they are. The sequence starts with zero, skips a few numbers and then increments by one.

Stella supports multi-load games, however, the set of ROM images must be combined into a single ROM image file. For example to create a multi-load ROM image file for Survival Island you would do the following under Unix:

   % cat survivl0.bin survivl6.bin survivl7.bin > survivl.bin
or to create it under DOS you would:
   % copy /b survivl0.bin+survivl6.bin+survivl7.bin survivl.bin

Once you have the multi-load ROM image file, survivl.bin in this case, you can play the game using it.

Supported File formats

Stella supports ROMs ending with extensions .a26, .bin, .rom, .gz, and .zip. For the last two compressed formats (GZIP and ZIP, respectively), Stella will automatically decompress the archive, and use the first ROM image it finds in it (ie, the first one ending in a valid extension). If a ZIP archive contains many such files, Stella will display a virtual filesystem of the contents of the archive.

Other extensions are also possible, namely to force a specific bankswitch scheme. Normally, the bankswitching scheme for a ROM is determined automatically, or manually by setting a ROM property, and you never have to do anything yourself. However, it is also possible to force the bankswitch type to use by adding a special filename extension. These extensions are listed in the ROM properties section under Cart.Type -> File Extension.

Note: These extensions are the same as those used by the Harmony Cart and Unocart and are not case-sensitive, so you can name your files and have them work across all applications. Again, to be clear, this is only necessary when you want to override the default bankswitching scheme for a ROM. This will not normally be necessary.

Playing a Game

Once Stella is installed and you have some ROM images you're almost ready to start playing.

Integrated GUI

Stella contains an integrated GUI for all ports. Commandline support is also available for those who want to use it.

If you start Stella and do not specify a ROM image, it will start in 'ROM Launcher' mode:

If this is your first time starting Stella, you may have to navigate to your ROMs. The path of the first ROM you play automatically defines the default ROM path. You can change it later in the ROM Launcher dialog.

At this point, you may want to set the locations for snapshots. This is described in more detail in Advanced Configuration - Snapshot Settings. These settings are optional, and can be left at the defaults if you won't be using snapshots in the ROM launcher.

You can start emulation by selecting a ROM and pressing 'Enter' or clicking 'Select', or double-clicking a ROM. Note that some games require you to 'Reset' the console before you start playing. In this case, you need to hit the virtual reset switch, which by default is the F2 key. Also, some games may require that you press the joystick fire button to begin, which by default is the Left Control or Space key(s), or button 0 on your joystick. If a game uses a more complex controller, see Getting Started - Keyboard Layout for more information. To exit a game and re-enter the ROM launcher, press the 'Escape' key.

Using the 'Search' textbox in the upper-right of the ROM launcher, the listing can be narrowed down, showing only the ROMs that match the pattern you enter.

While the file listing is in focus, you can type some characters, and the listing will 'jump' to the file that matches what you typed. This is case-insensitive. Hold down the Shift key on the first character to select directories instead. The delay between successive keypresses being treated as part of one word is controlled by the 'listdelay' option; see User Interface Settings to change this setting.

Command Menu

While playing a game, normally one would use the keyboard shortcuts for controlling the 'virtual' switches in Stella (ie, the commands associated with the function keys as described in Getting Started - Keyboard Layout). However, another alternative is available. Pressing the '\' key toggles a command menu dialog as follows:

This dialog contains a set of buttons that represent the same functionality as the function keys and display the current state. You may find this useful if you cannot remember all the function key events, or you wish to use Stella without a keyboard (ie, in a standalone gaming system).

Keyboard Layout

The Atari 2600 console controls and controllers are mapped to the computer's keyboard as shown in the following tables. However, most of these events can be remapped to other keys on your keyboard or buttons on your joystick (see Advanced Configuration - Event Remapping). The tables below show the default settings.

Note: All key names are based on the US QWERTY keyboard layout.. If you use a different layout some keys may differ. You can use the following layout image as reference where to find the US keys on your keyboard.


Console Controls (can be remapped)

Function Key (Standard) Key (macOS)
Exit emulator Control + q Cmd + q
Exit game mode/enter launcher mode Escape Escape
Enter/exit options mode Tab/Escape Tab/Escape
Enter/exit command mode Backslash (\) Backslash (\)
Enter/exit debugger Backquote (`) Backquote (`)
Select Game F1 F1
Reset Game F2 F2
Color TV F3 F3
Black/White TV F4 F4
Left Player Difficulty A F5 F5
Left Player Difficulty B F6 F6
Right Player Difficulty A F7 F7
Right Player Difficulty B F8 F8
Save state to current slot F9 F9
Save all Time Machine states Alt + F9 Cmd + F9
Change to previous state slot Shift + F10 Shift + F10
Change to next state slot F10 F10
Automatically change state slot Alt + F10 Cmd + F10
Load state from current slot F11 F11
Load all states into Time Machine Alt + F11 Cmd + F11
Save PNG snapshot F12 F12
Pause/resume emulation Pause Shift-Cmd + p

Joystick/BoosterGrip Controller (can be remapped)

Left Joystick (Joy0) Right Joystick (Joy1)
Function Key
Joystick Up Up arrow
Joystick Down Down arrow
Joystick Left Left arrow
Joystick Right Right arrow
Fire Button Left Control, Space
Top Booster Button 4
Handle Grip Trigger 5
Function Key
Joystick Up Y
Joystick Down H
Joystick Left G
Joystick Right J
Fire Button F
Top Booster Button 6
Handle Grip Trigger 7

Sega Genesis Controller (cannot be remapped, always associated with joystick and booster-grip controllers)

Left Pad Right Pad
Function Key
Pad Up Same as 'Joy0 Up'
Pad Down Same as 'Joy0 Down'
Pad Left Same as 'Joy0 Left'
Pad Right Same as 'Joy0 Right'
Button 'B' Same as 'Joy0 Fire'
Button 'C' Same as 'Joy0 Top Booster Button'
Function Key
Pad Up Same as 'Joy1 Up'
Pad Down Same as 'Joy1 Down'
Pad Left Same as 'Joy1 Left'
Pad Right Same as 'Joy1 Right'
Button 'B' Same as 'Joy1 Fire'
Button 'C' Same as 'Joy1 Top Booster Button'

Driving Controller (cannot be remapped, always associated with joystick controller)

Left Driving Right Driving
Function Key
Left Direction Same as 'Joy0 Left'
Right Direction Same as 'Joy0 Right'
Fire Button Same as 'Joy0 Fire'
Function Key
Left Direction Same as 'Joy1 Left'
Right Direction Same as 'Joy1 Right'
Fire Button Same as 'Joy1 Fire'

Trackball Controller (uses mouse, left port only)

Left Trackball
Function Key
Fire Button Same as 'Joy0 Fire'

Light Gun Controller (uses mouse, left port only)

Left Light Gun
Function Key
Fire Button Same as 'Joy0 Fire'

Paddle Controller digital emulation (can be remapped)

Left Paddles Right Paddles
Function Key
Paddle 0 Turn Left Left arrow
Paddle 0 Turn Right Right arrow
Paddle 0 Fire Left Control, Space
Paddle 1 Turn Left Up arrow
Paddle 1 Turn Right Down arrow
Paddle 1 Fire 4
Function Key
Paddle 2 Turn Left G
Paddle 2 Turn Right J
Paddle 2 Fire F
Paddle 3 Turn Left Y
Paddle 3 Turn Right H
Paddle 3 Fire 6

Keypad Controller (can be remapped)

Left Keypad Right Keypad
Pad Button Key
1 1
2 2
3 3
4 Q
5 W
6 E
7 A
8 S
9 D
. Z
0 X
# C
Pad Button Key
1 8
2 9
3 0
4 I
5 O
6 P
7 K
8 L
9 ;
. ,
0 .
# /

CompuMate Controller (cannot be remapped)

CompuMate Key
0 - 9 0 - 9
A - Z A - Z
Comma Comma
Period Period
Func Control (left or right)
Shift Shift (left or right)
Enter Return/Enter
Space Space
Func-Space Shift + Backspace
+ + or Shift + 1
- - or Shift + 2
* Shift + 3
/ / or Shift + 4
= = or Shift + 5
? ? (Shift + /) or Shift + 6
$ Shift + 7
[ [ or Shift + 8
] ] or Shift + 9
" " (Shift + ') or Shift + 0

Audio & Video Keys (can be remapped)

Function Key (Standard) Key (macOS)
Toggle sound Control + ] Control + ]
Decrease volume Alt + [ Cmd + [
Increase volume Alt + ] Cmd + ]
Switch to next larger zoom level in windowed mode,
toggle stretching in fullscreen mode
Alt + = Cmd + =
Switch to next smaller zoom level in windowed mode,
toggle stretching in fullscreen mode
Alt + - Cmd + -
Toggle windowed/fullscreen mode Alt + Enter Cmd + Enter
Toggle adapting display refresh rate to game frame rate
Note: Not available for macOS.
Alt + r Cmd + r
Decrease overscan in fullscreen mode Shift + PageDown Shift-Fn + Down arrow
Increase overscan in fullscreen mode Shift + PageUp Shift-Fn + Up arrow
Move display down (uses "Display.VCenter") Alt + PageDown Cmd-Fn + Down arrow
Move display up (uses "Display.VCenter") Alt + PageUp Cmd-Fn + Up arrow
Decrease vertical display size Shift-Alt + PageUp Shift-Cmd-Fn + Up arrow
Increase vertical display size Shift-Alt + PageDown Shift-Cmd-Fn + Down arrow
Switch to previous display format (NTSC/PAL/SECAM etc.) Shift-Control + f Shift-Control + f
Switch to next display format (NTSC/PAL/SECAM etc.) Control + f Control + f
Toggle display interpolation Control + i Control + i
These settings can also be changed using Global Audio & Video Keys

Palettes Keys (can be remapped)

Function Key (Standard) Key (macOS)
Select previous palette (Standard/z26/User/Custom) Shift-Control + p Shift-Control + p
Select next palette (Standard/z26/User/Custom) Control + p Control + p
Select previous palette attribute Shift-Alt + 9 Shift-Cmd + 9
Select next palette attribute Alt + 9 Cmd + 9
Decrease selected palette attribute Shift-Alt + 0 Shift-Cmd + 0
Increase selected palette attribute Alt + 0 Cmd + 0
These settings can also be changed using Global Audio & Video Keys

TV effects Keys (can be remapped)

Function Key (Standard) Key (macOS)
Select previous TV effects preset Shift-Alt + 1 Shift-Cmd + 1
Select next TV effects preset Alt + 1 Cmd + 1
Select previous 'Custom' mode attribute (*) Shift-Alt + 2 Shift-Cmd + 2
Select next 'Custom' mode attribute (*) Alt + 2 Cmd + 2
Decrease 'Custom' selected attribute value (*) Shift-Alt + 3 Shift-Cmd + 3
Increase 'Custom' selected attribute value (*) Alt + 3 Cmd + 3
Toggle 'phosphor' mode Alt + p Cmd + p
Decrease 'phosphor' blend Shift-Alt + 4 Shift-Cmd + 4
Increase 'phosphor' blend Alt + 4 Cmd + 4
Decrease scanline intensity Shift-Alt + 5 Shift-Cmd + 5
Increase scanline intensity Alt + 5 Cmd + 5
These settings can also be changed using Global Audio & Video Keys
Items marked as (*) will also switch to 'Custom' mode

Global Audio & Video Keys (can be remapped)

These keys allow selecting and changing audio & video settings without having to remember the dedicated keys.

Function Key (Standard) Key (macOS)
Select previous AV setting End Fn + Left arrow
Select next AV setting Home Fn + Right arrow
Decrease current AV setting PageDown Fn + Down arrow
Increase current AV setting PageUp Fn + Up arrow


Developer Keys (can be remapped)

Function Key (Standard) Key (macOS)
Toggle frame stats
(scanline count/FPS/BS type etc.)
Alt + L Cmd + L
Toggle TIA Player0 object Alt + z Cmd + z
Toggle TIA Player1 object Alt + x Cmd + x
Toggle TIA Missile0 object Alt + c Cmd + c
Toggle TIA Missile1 object Alt + v Cmd + v
Toggle TIA Ball object Alt + b Cmd + b
Toggle TIA Playfield object Alt + n Cmd + n
Toggle all TIA objects Alt + Comma Cmd + Comma
Toggle TIA Player0 collisions Shift-Alt + z Shift-Cmd + z
Toggle TIA Player1 collisions Shift-Alt + x Shift-Cmd + x
Toggle TIA Missile0 collisions Shift-Alt + c Shift-Cmd + c
Toggle TIA Missile1 collisions Shift-Alt + v Shift-Cmd + v
Toggle TIA Ball collisions Shift-Alt + b Shift-Cmd + b
Toggle TIA Playfield collisions Shift-Alt + n Shift-Cmd + n
Toggle all TIA collisions Shift-Alt + Comma Shift-Cmd + Comma
Toggle TIA 'Fixed Debug Colors' mode Alt + . Cmd + .
Toggle PAL color-loss effect Control + L Control + L
Toggle TV 'Jitter' effect Alt + j Cmd + j

Other Emulation Keys (can be remapped)

Function Key (Standard) Key (macOS)
Toggle 'Turbo' mode Control + t Control + t
Switch mouse between controller emulation modes
(see Game Properties - Controller)
Control + 0 Control + 0
Toggle grab mouse Control + g Control + g
Swap Stelladaptor/2600-daptor port ordering Control + 1 Control + 1
Load previous game in ROM (multicart ROM, TIA mode) Shift-Control + r Shift-Control + r
Reload current ROM (singlecart ROM, TIA mode)
Load next game in ROM (multicart ROM, TIA mode)
Control + r Control + r
Reload ROM listing (ROM launcher mode) Control + r Control + r
Emulate 'frying' effect (TIA mode) Backspace Backspace
Go to parent directory (UI mode) Backspace Backspace
Save continuous PNG snapshots
(per interval defined in Snapshot Settings)
Alt + s Cmd + s
Save continuous PNG snapshots (every frame) Shift-Alt + s Shift-Cmd + s
Toggle 'Time Machine' mode Alt + t Cmd + t
Enter/Exit the Time Machine dialog t to enter, t/Escape/Space to exit t to enter, t/Escape/Space to exit
Rewind by one state (enters the Time Machine dialog) Alt + Left arrow Cmd + Left arrow
Rewind by 10 states (enters the Time Machine dialog) Shift-Alt + Left arrow Shift-Cmd + Left arrow
Rewind all states (enters the Time Machine dialog) Alt + Down arrow Cmd + Down arrow
Unwind by one state (enters the Time Machine dialog) Alt + Right arrow Cmd + Right arrow
Unwind by 10 states (enters the Time Machine dialog) Shift-Alt + Right arrow Shift-Cmd + Right arrow
Unwind all states (enters the Time Machine dialog) Alt + Up arrow Cmd + Up arrow

UI Keys in Text Editing areas (cannot be remapped)

KeyEditor Function
HomeMove cursor to beginning of line
EndMove cursor to end of line
DeleteRemove character to right of cursor
BackspaceRemove character to left of cursor
Control-aSame function as 'Home'
Control-eSame function as 'End'
Control-dSame function as 'Delete'
Control-kRemove all characters from cursor to end of line
Control-uRemove all characters from cursor to beginning of line
Control-wRemove entire word to left of cursor
Control-LeftMove cursor to beginning of word to the left
Control-RightMove cursor to beginning of word to the right
Control-cCopy entire line to clipboard (not complete)
Control-vPaste clipboard contents (not complete)

Controller Map

Some Atari (virtual) controllers are simulated with more than one computer controller, and there are several special cases where controllers are active in certain modes only, as the table below shows. Items marked as (+ extra) indicate that the computer controller may not have enough buttons/axes etc. to fully emulate the device, so extra functionality must be mapped to other controllers.

Keyboard Joystick Mouse
(auto mode)
(specific axis)
Booster ✓ (+ extra) ✓ (+ extra)
Genesis ✓ (+ extra)
Keyboard ✓ (+ extra) ✓ (2600-daptor II)
Trackball/Mouse ✓ (axis ignored)
Light Gun ✓ (axis ignored)
Mindlink ✓ (axis ignored)
AtariVox N/A N/A N/A N/A voice (2600-daptor II)
SaveKey N/A N/A N/A N/A N/A

Stella's 'Time Machine'

A special feature of Stella is the 'Time Machine' mode. In this mode, Stella automatically creates savestates in regular, user-defined intervals. At any time, the user can interrupt the current emulation and navigate back and forth within the saved timeline. This can be done either by using the Time Machine hotkeys described in Hotkeys - Other Keys or by using the Time Machine dialog. This dialog is automatically entered when using one of the Time Machine hotkeys. The hotkeys continue to function within the dialog.

Time Machine dialog:

The dialog items are explained in the following two tables.

Top row (left to right)

Current stateShows the currently loaded state's number
'Timeline' sliderShows the position of the current state in the recorded timeline. A state can be selected by dragging the slider with the mouse. To visualize state compression, small marks split the timeline into five, equally sized state number intervals.
Total statesShows the total number of save states in the Time Machine

Bottom row (left to right)

Current timeShows the time of the currently selected status, relative to the first one
'Start/Stop' buttonStarts or stops the Time Machine
'Continue' buttonExits the dialog and continues emulation
'Rewind All' buttonNavigates back to the begin of the timeline
'Rewind One' buttonNavigates back by one state
'Unwind One' buttonNavigates forward by one state
'Unwind All' buttonNavigates forward to the end of the timeline
'Save All' buttonSaves all Time Machine states to disk
'Load All' buttonLoades all states from disk into Time Machine
Navigation infoInforms about the interval of the user's last Time Machine navigation. The interval can vary if the timeline is compressed.
Total timeShows the total time covered by the save states (aka 'Horizon')

The 'Time Machine' mode can be configured by the user. For details see Developer Options - Time Machine tab.

Advanced Configuration

The default options in Stella are meant to cater to as many situations as possible. As such, you may never need to change many of its options. However, Stella is very configurable, and if you want to change its behaviour in some way, there's likely a configuration option to do so. The remainder of this (lengthy) section details every configurable option.

Using the Command Line

In addition to the built in ROM launcher, Stella can also be used from the commandline (assuming your operating system has a commandline).

To run Stella from the commandline, use the following format:

   stella [options ...] ROM_FILENAME

Options ('0' or 'false' indicates false, '1' or 'true' indicates true, others are self-explanatory):

Argument Description
-video <direct3d|opengl|opengles2|opengles|software>
Use the given rendering backend (where applicable); default is the best available mode detected.
-vsync <1|0>
Synchronize screen updates to the vertical blank period. This can result in smoother updates, and eliminate tearing.
-fullscreen <1|0>
Enable fullscreen mode.
-center <1|0>
Centers all windows (if possible).
-windowedpos <XxY>
Sets the window position in windowed emulator mode.
-display <number>
Sets the display for Stella's emulator.
-palette <standard|z26|user|custom>
Set the palette to either normal Stella, the one used in the z26 emulator, a user-defined palette, or a custom palette generated from user-defined phase shifts.
-pal.phase_ntsc <number>
Adjust phase shift of 'custom' NTSC palette.
-pal.phase_pal <number>
Adjust phase shift of 'custom' PAL palette.
-pal.hue <number>
Adjust hue of current palette (range -1.0 to 1.0).
-pal.saturation <number>
Adjust saturation of current palette (range -1.0 to 1.0).
-pal.contrast <number>
Adjust contrast of current palette (range -1.0 to 1.0).
-pal.brightness <number>
Adjust brightness of current palette (range -1.0 to 1.0).
-pal.gamma <number>
Adjust gamma of current palette (range -1.0 to 1.0).
-speed <number>
Control the emulation speed (as a percentage, 10 - 1000).
-turbo <1|0>
Enable 'Turbo' mode for maximum emulation speed.
-uimessages <1|0>
Enable or disable display of message in the UI. Note that messages indicating serious errors override this setting, and are always shown.
-audio.enabled <1|0>
Enable or disable sound generation.
-audio.volume <0 - 100>
Set the volume.
-audio.preset <1 - 5>
Set an audio preset. Numbers in sequence represent presets for 'custom', 'low quality, medium lag', 'high quality, medium lag', 'high quality, low lag' and 'ultra quality, minimal lag'.
-audio.fragment_size <128|256|512|1024|2048|4096>
Set the number of samples in a single fragment processed by the audio driver.
-audio.sample_rate <44100|48000|96000>
Set sound sample output frequency.
-audio.resampling_quality <1|2|3>
Set resampling quality to low (1), high (2) or ultra (3).
-audio.headroom <0 - 20>
Set number of additional half-frames to prebuffer.
-audio.buffer_size <0 - 20>
Set maximum number of additional half-frames to buffer.
-audio.stereo <1|0>
Enable or disable stereo mode for all ROMs.
-audio.dpc_pitch <10000 - 30000>
Set the pitch of Pitfall II music.
-tia.zoom <zoom>
Use the specified zoom level (integer) while in TIA/emulation mode.
-tia.vsizeadjust <-5 - 5>
Adjust the display height of the TIA image
-tia.inter <1|0>
Use interpolation for the TIA image (results in blending/smoothing of the image).
-tia.fs_stretch <1|0>
Stretch TIA image completely while in fullscreen mode, vs. keeping the correct aspect ratio.
-tia.fs_refresh <1|0>
While in fullscreen mode, adapt the display's refresh rate to the game's frame rate to minimize judder.
Note: Not available for macOS.
-tia.fs_overscan <0 - 10>
Add overscan to TIA image while in fullscreen mode
-tia.dbgcolors <roygbp>
Assigns the colours (R)ed, (O)range, (Y)ellow, (G)reen, (B)lue and (P)urple to each graphical register P0/M0/P1/M1/PF/BL, respectively. Currently, these change be changed around to apply different colours to the respective register.
-tv.filter <0 - 5>
Blargg TV effects, 0 is disabled, next numbers in sequence represent presets for 'RGB', 'S-Video', 'Composite', 'Bad Adjust' and 'Custom' modes.
-tv.sharpness <number>
Blargg TV effects 'sharpness' (only available in custom mode, range -1.0 to 1.0).
-tv.resolution <number>
Blargg TV effects 'resolution' (only available in custom mode, range -1.0 to 1.0).
-tv.artifacts <number>
Blargg TV effects 'artifacts' (only available in custom mode, range -1.0 to 1.0).
-tv.fringing <number>
Blargg TV effects 'fringing' (only available in custom mode, range -1.0 to 1.0).
-tv.bleed <number>
Blargg TV effects 'bleed' (only available in custom mode, range -1.0 to 1.0).
-tv.phosphor <always|byrom>
Determines how phosphor mode is enabled. If 'always', then the ROM properties entry is ignored, and phosphor mode is always turned on. Otherwise, the ROM properties determine whether phosphor mode is used for each ROM.
-tv.phosblend <0 - 100>
Enable phosphor blending level; 0 implies no mixing, and 100 is full mixing (not recommended). Note that this doesn't actually enable phosphor mode; that is done for each ROM in the ROM properties. Higher blend values will intensify the phosphor effect. Depending on your display and personal preferences, the optimal default for you may vary. Slow LCDs (especially for office use) may only need a low blend of around 30, while fast switching gamer LCDs may need about 70 to look similar to a CRT.
-tv.scanlines <0 - 100>
TV effects scanline intensity, where 0 means completely off. Note: No scanlines in 1x mode snapshots.
-cheat <code>
Use the specified cheatcode (see Cheat section for description).
-loglevel <0|1|2>
Indicates level of logging to perform while the application is running. Zero completely disables logging (except for serious errors), while the remaining numbers show increasingly more detail.
-logtoconsole <1|0>
Indicates that logged output should be printed to the console/commandline as it's being collected. An internal log will still be kept, and the amount of logging is still controlled by 'loglevel'.
-joydeadzone <number>
Sets the joystick axis deadzone area for analog joysticks/gamepads. All values within the deadzone are treated as zero-axis values, while only those values outside are registered as valid input. Accepts a number from 0 - 29, and uses the formula 3200 + number * 1000. So the possible deadzone values range from 3200 to 32200.
-psense <number>
Sensitivity for emulation of paddles when using analog paddles. Valid range of values is from 1 to 30, with larger numbers causing faster movement.
-dejitter.base <0 - 10>
Strength of paddle input averaging.
-dejitter.diff <0 - 10>
Impact of fast paddle movement on input averaging.
-dcsense <number>
Sensitivity for emulation of driving controllers when using a mouse. Valid range of values is from 1 to 20, with larger numbers causing faster movement.
-joyallow4 <1|0>
Allow all 4 directions on a joystick to be pressed simultaneously.
-modcombo <1|0>
Use modifier(Shift/Alt/Control)-x key combos. This is normally enabled, since the 'Quit' command is tied to 'Control-q'. However, there are times when you want to disable them.
E.g. a 2-player game is using either the 'f' or 'r' keys for movement, and pressing Control (for Fire) will perform an unwanted action associated with Control-r or Control-f default keys.
-saport <lr|rl>
Determines how to enumerate the Stelladaptor/2600-daptor devices in the order they are found: 'lr' means first is left port, second is right port, 'rl' means the opposite.
-avoxport <name>
Set the name of the serial port where an AtariVox is connected.
-usemouse <always|analog|never>
Use mouse as a controller as specified by ROM properties in specific case. Always and never are self-explanatory, analog means only for analog-type devices (paddles, trackball, etc.).
-msense <number>
Sensitivity for emulation of paddles when using a mouse. Valid range of values is from 1 to 20, with larger numbers causing faster movement.
-tsense <number>
Sensitivity for emulation of trackball controllers when using a mouse. Valid range of values is from 1 to 20, with larger numbers causing faster movement.
-dsense <number>
Sensitivity for emulation of paddles when using a digital device (ie, joystick digital axis or button, keyboard key, etc.). Valid range of values is from 1 to 20, with larger numbers causing faster movement.
-cursor <0|1|2|3>
Set mouse cursor state in UI/emulation modes.
-grabmouse <1|0>
Locks the mouse cursor in the game window in emulation mode.
-autoslot <1|0>
Automatically change to the next available save state slot after saving a ROM state file.
-saveonexit <none|current|all>
Automatically save no, current or all states when exiting emulation. The latter also loads all states when entering emulation.
-fastscbios <1|0>
Disable Supercharger BIOS progress loading bars.
-threads <1|0>
Enable multi-threaded video rendering (may not improve performance on all systems).
-snapsavedir <path>
The directory to save snapshot files to.
-snaploaddir <path>
The directory to load ROM info viewer snaposhot files from.
-snapname <int|rom>
When saving snapshots, use either the internal database name or the actual ROM filename.
-sssingle <1|0>
Generate single snapshot instead of many, overwriting any previous snapshots.
-ss1x <1|0>
Ignore any scaling applied to the TIA image, and save snapshot in unscaled (1x) mode.
-ssinterval <number>
Set the interval in seconds between taking snapshots in continuous snapshot mode (currently 1 - 10).
-rominfo <rom>
Display detailed information about the given ROM, and then exit Stella.
Prints relevant contents of the Stella ROM database, one ROM per line, and then exit Stella. This can be used for external frontends.
-exitlauncher <1|0>
Always exit to ROM launcher when exiting a ROM (normally, an exit to launcher only happens when started with the launcher).
-launcherpos <XxY>
Sets the window position in windowed ROM launcher mode.
-launcherdisplay <number>
Sets the display for the ROM launcher.
-launcherres <WxH>
Set the size of the ROM launcher.
-launcherfont <small|low_medium|medium|large|large12|large14|large16>
Set the size of the font in the ROM launcher.
-launcherroms <1|0>
Specifies whether to show ROMs only (the default) or all files in the ROM launcher.
-romviewer <float>
Hide ROM Info Viewer in ROM launcher mode (0) or use the given zoom level.
Note: The zoom level is converted into a percentage in the UI.
-uipalette <standard|classic|light>
Use the specified palette for UI elements.
-dialogfont <small|low_medium|medium|large|large12|large14|large16>
Set the size of the font in the dialogs.
-dialogpos <0 - 4>
Set the position of dialogs within Stella windows (0 = center).
-hidpi <0|1>
Enables the HiDPI mode which scales the UI by a factor of two.
-confirmexit <0|1>
Display a popup when emulation is exited.
-listdelay <delay>
Set the amount of time to wait between treating successive keypresses as a single word in file listings (value can range from 300-1000). Use '0' to disable list-skipping completely.
-mwheel <lines>
Set the number of lines the mousewheel will scroll in the UI (1 - 10).
-mdouble <speed>
Set the mouse double click speed in the UI (100 - 900 ms).
-ctrldelay <delay>
Set the delay before controller input will start repeating in the UI (200 - 1000 ms).
-ctrlrate <rate>
Set the controller repeat rate in the UI (2 - 30 repeats/s).
-romdir <dir>
Set the path where the ROM launcher will start.
-followlauncher <0|1>
Make the start path follow ROM launcher navigation.
-maxres <WxH>
Useful for developers, this sets the maximum size of window that can be created, allowing to simulate testing on 'smaller' systems.
-basedir <dir>
Override the base directory for all config files.
Override the base directory for all config files by attempting to use the application directory. For now this is only supported in Windows.
Prints a help message describing these options, and then exit Stella.

The following are useful to developers. Only use them if you know what you're doing! Note that in all cases, the values supplied to the arguments are not case sensitive.

Argument Description
-dis.resolve <1|0>
Try to differentiate between code vs. data sections in the disassembler. See the Debugger - ROM Disassembly Settings for more information.
-dis.gfxformat <2|16>
Sets the base to use for displaying GFX sections in the disassembler.
-dis.showaddr <1|0>
Shows/hides opcode addresses in the disassembler.
-dis.relocate <1|0>
Relocate calls out of address range in the disassembler.
-dbg.pos <XxY>
Sets the window position in windowed debugger mode.
-dbg.display <number>
Sets the display for the debugger.
-dbg.res <WxH>
Set the size of the debugger window.
-dbg.fontsize <small|medium|large|>
Set the font size in the debugger window.
-dbg.fontstyle <0|1|2|3>
How to use bold fonts in the debugger window. '0' means all normal font, '1' is bold labels only, '2' is bold non-labels only, '3' is all bold font.
-dbg.ghostreadstrap <1|0>
Debugger considers/ignores 'ghost' reads for trap addresses
-dbg.uhex <0|1>
Lower-/uppercase HEX display
-break <address>
Set a breakpoint at specified address.
Immediately jump to debugger mode when starting Stella.
-holdjoy0 <U,D,L,R,F>
Start the emulator with the left joystick direction/button held down (ie, use 'UF' for up and fire). After entering the emulation, you will have to press and release the direction again to release the event.
-holdjoy1 <U,D,L,R,F>
Start the emulator with the right joystick direction/button held down (ie, use 'UF' for up and fire). After entering the emulation, you will have to press and release the direction again to release the event.
Start the emulator with the Game Select switch held down. After entering the emulation, you will have to press and release 'Select' to release the event.
Start the emulator with the Game Reset switch held down. After entering the emulation, you will have to press and release 'Reset' to release the event.
-bs <type>
Set "Cart.Type" property. See the Game Properties section for valid types.
-type <type>
Same as using -bs.
-startbank <bank>
Set "Cart.StartBank" property.
-channels <Mono|Stereo>
Set "Cart.Sound" property.
-ld <A|B>
Set "Console.LeftDiff" property.
-rd <A|B>
Set "Console.RightDiff" property.
-tv <Color|BW>
Set "Console.TVType" property.
-sp <Yes|No>
Set "Console.SwapPorts" property.
-lc <type>
Set "Controller.Left" property. See the Game Properties section for valid types.
-rc <type>
Set "Controller.Right" property. See the Game Properties section for valid types.
-bc <type>
Sets both "Controller.Left" and "Controller.Right" properties. See the Game Properties section for valid types.
-cp <Yes|No>
Set "Controller.SwapPaddles" property.
-pxcenter <-10..30>
Set "Controller.PaddlesXCenter" property.
-pycenter <-10..30>
Set "Controller.PaddlesYCenter" property.
-ma <Auto|XY>
Set "Controller.MouseAxis" property. See the Game Properties section for valid types.
-format <format>
Set "Display.Format" property. See the Game Properties section for valid formats.
-vcenter <number>
Set "Display.VCenter" property (-5..5).
-pp <Yes|No>
Set "Display.Phosphor" property.
-ppblend <number>
Set "Display.PPBlend" property, used for phosphor effect (0-100). Default is whatever is specified for tv.phosblend.

The following are almost all available in two sets, one for players (prefixed by "plr.") and one for developers (prefixd by "dev."). Only use them if you know what you're doing! Note that in all cases, the values supplied to the arguments are not case sensitive.

Argument Description
-dev.settings <1|0>
Select developer (1) or player (0) set.
-<plr.|dev.>stats <1|0>
Overlay console info on the TIA image during emulation.
-<plr.|dev.>console <2600|7800>
Select console for B/W and Pause key handling and RAM initialization.
-<plr.|dev.>bankrandom <1|0>
On reset, randomize the startup bank (only for selected bankswitch types).
-<plr.|dev.>ramrandom <1|0>
On reset, either randomize all RAM content, or initialize with zero (console = 2600)/startup values (console = 7800) instead.
-<plr.|dev.>cpurandom <S,A,X,Y,P>
On reset, randomize the content of the specified CPU registers.
-dev.tiadriven <1|0>
Set unused TIA pins to be randomly driven high or low on a read/peek. If disabled, use the last databus value for those pins instead.
-dev.rwportbreak <1|0>
Since the 2600 has no dedicated R/W line, different addresses are used for RAM read or write access.
If the code reads from such a write address, this causes an unwanted, semi-random write to that address.
When this option is enabled, such reads interrupt emulation and the debugger is entered.
-dev.wrportbreak <1|0>
Same as above.
If the code writes to such a read address, nothing happens. But a developer should be made aware of it, because this indicates a problem with the code.
When this option is enabled, such writes interrupt emulation and the debugger is entered.
-dev.thumb.trapfatal <1|0>
When enabled, this allows the Thumb ARM emulation to throw an exception and enter the debugger on fatal errors. When disabled, such fatal errors are simply logged, and emulation continues. Do not use this unless you know exactly what you're doing, as it changes the behaviour as compared to real hardware.
-<plr.|dev.>eepromaccess <1|0>
When enabled, each read or write access to the AtariVox/SaveKey EEPROM is signalled by a message.
-dev.tia.type <standard|koolaidman|
Set emulated TIA type.
-dev.tia.plinvphase <1|0>
Enable/disable inverted HMOVE clock phase for players (Kool Aid Man glitch).
-dev.tia.msinvphase <1|0>
Enable/disable inverted HMOVE clock phase for missiles (Cosmic Ark stars glitch).
-dev.tia.blinvphase <1|0>
Enable/disable inverted HMOVE clock phase for ball.
-dev.tia.delaypfbits <1|0>
Enable/disable playfield bits delayed by one color clock (stray playfield pixels in Pesco).
-dev.tia.delaypfcolor <1|0>
Enable/disable playfield color delayed by one color clock (colored step borders in Quick Step!).
-dev.tia.delayplswap <1|0>
Enable/disable player swap delayed by one color clock (He-Man title glitch).
-dev.tia.delayblswap <1|0>
Enable/disable ball swap delayed by one color clock.
-<plr.|dev.>tv.jitter <1|0>
Enable TV jitter/roll effect, when there are too many or too few scanlines per frame.
-<plr.|dev.>tv.jitter_recovery <1 - 20>
When TV jitter/roll effect is enabled, determines how long to delay recovery time (recovery spread over multiple frames).
-<plr.|dev.>colorloss <1|0>
Enable/disable the PAL color-loss effect.
-<plr.|dev.>debugcolors <1|0>
Enable/disable the fixed debug colors.
-<plr.|dev.>timemachine <1|0>
Enable/disable the Time Machine
-<plr.|dev.>tm.size <20 - 1000>
Define the Time Machine buffer size.
-<plr.|dev.>tm.uncompressed <0 - 1000>
Define the uncompressed Time Machine buffer size. Must be <= Time Machine buffer size.
-<plr.|dev.>tm.interval <1f|3f|10f|30f|
Define the interval between two save states.
-<plr.|dev.>tm.horizon <3s|10s|30s|1m|3m|
Define the horizon of the Time Machine.

Changing Options

All settings can be changed within the integrated Options UI while Stella is running (unless otherwise noted; some settings require an application restart). The Options menu can be accessed from the ROM launcher by clicking the Options button, or in-game by pressing the 'Tab' key.

Options Menu dialog:

Video & Audio Settings dialog (Display):

ItemBrief descriptionFor more information,
see CommandLine
RendererUse specified rendering mode-video
InterpolationEnable interpolation of the TIA image-tia.inter
ZoomZoom level of the TIA image-tia.zoom
FullscreenSelf-explanatory - Note that colors may slightly change. This depends on the OS and renderer used.-fullscreen
StretchIn fullscreen mode, completely fill screen with the TIA image.-tia.fs_stretch
Adapt display...In fullscreen mode, adapt the display's refresh rate to the game's frame rate to minimize judder.
Note: Not available for macOS.
OverscanIn fullscreen mode, add overscan to the TIA image-tia.fs_overscan
V-Size adjustAdjust height of the TIA image-tia.vsizeadjust

Video & Audio Settings dialog (Palettes):

ItemBrief descriptionFor more information,
see CommandLine
PalettePalette used for emulation mode-palette
NTSC phaseAdjust phase shift for 'Custom' NTSC palette-pal.phase_ntsc
PAL phaseAdjust phase shift for 'Custom' PAL palette-pal.phase_pal
HueAdjust hue of currently selected palette-pal.hue
SaturationAdjust saturation of currently selected palette-pal.saturation
ContrastAdjust contrast of currently selected palette-pal.contrast
BrightnessAdjust brightness of currently selected palette-pal.brightness
GammaAdjust gamma of currently selected palette-pal.gamma

Video & Audio Settings dialog (TV Effects):

ItemBrief descriptionFor more information,
see CommandLine
TV modeDisable TV effects, or select TV preset-tv.filter
Adjustable slidersSet specific attribute in 'Custom' TV mode-tv.sharpness, -tv.resolution, etc.
Phosphor for all ROMsEnable phosphor mode for all ROMs-tv.phosphor
Blend (phosphor)Blend level to use in phosphor mode for all ROMs (needs to be manually adjusted for your particular hardware)-tv.phosblend
Scanline intensitySets scanline black-level intensity.
Note: No scanlines in 1x mode snapshots.
Clone RGBCopy 'RGB' attributes to 'Custom' TV mode sliders 
Clone S-VideoCopy 'S-Video' attributes to 'Custom' TV mode sliders 
Clone CompositeCopy 'Composite' attributes to 'Custom' TV mode sliders 
Clone Bad adjustCopy 'Bad Adjust' attributes to 'Custom' TV mode sliders 
RevertRevert attribute sliders to saved 'Custom' TV mode settings 

Video & Audio Settings dialog (Audio):

ItemBrief descriptionFor more information,
see CommandLine
Enable audioSelf-explanatory-audio.enabled
ModeSelect an audio preset or choose 'custom' for manual configuration-audio.preset
Fragment sizeThe number of samples in a single fragment processed by the audio driver. Smaller values mean less latency, but may lead to dropouts (depending on OS and hardware).-audio.fragment_size
Sample rate Output samples per second. Higher values reduce artifacts from resampling and decrease latency, but may lead to dropouts (depending on OS and hardware). -audio.sample_rate
Resampling quality Chooses the algorithm used for resampling (= converting TIA output to the target sample rate). 'High' and 'ultra' use a high-quality Lanczos filter but require slightly more CPU, while 'low' may lead to audible screeching artifacts in some games (notably Quadrun). -audio.resampling_quality
HeadroomNumber of frames to buffer before playback starts. Higher values increase latency, but reduce the potential for dropouts.-audio.headroom
Buffer sizeMaximum size of the audio buffer. Higher values increase maximum latency, but reduce the potential for dropouts-audio.buffer_size
Stereo for all ROMsEnable stereo mode for all ROMs.-audio.stereo
Pitfall II music pitchDefines the pitch of Pitfall II music (which may vary between carts).-audio.dpc_pitch

IMPORTANT: In order to maintain a stable stream of audio data, emulation speed must be synchronized with the audio hardware. Buffering happens in multiple places (OS = fragment size, Stella = headroom and buffer size) and improves the tolerance to speed fluctuations, but introduces latency which manifests as a lag between audio and video.

Too aggressive settings for your combination of hardware and software (high sample rate, low fragment size, low headroom, low buffer size) may lead to audio dropouts whose effect may range from isolated popping artifacts to garbled audio. You can check the system log for related messages. If you get recurring messages about audio overruns and underruns (isolates underruns / overruns are normal and a consequence of host system activity), you might have to adjust your settings.

Emulation dialog:

ItemBrief descriptionFor more information,
see CommandLine
Emulation speedEmulation speed-speed
VSyncEnable vertical synced updates-vsync
TurboEnable 'Turbo' mode for maximum emulation speed. This overwrites 'Emulation speed' setting and disables 'VSync'.-turbo
Multi-threadingEnable multi-threaded rendering-threads
Fast SuperCharger loadSkip progress loading bars for SuperCharger ROMs-fastscbios
Show UI messagesOverlay UI messages onscreen-uimessages
Confirm exiting...Display a popup when emulation is exited-confirmexit
When entering/exiting emulation: Automatically save no, current or all Time Machine states when exiting emulation.
The latter also loads all states when entering emulation. When this is enabled, you can always continue your game session from where you exited it. Even including the Time Machine buffer!
Automatically change... Automatically change to the next available save state slot after saving a ROM state file. -autoslot

Input Settings dialog:

This dialog is described in further detail in Advanced Configuration - Event Remapping.

User Interface Settings dialog (2 tabs):

ItemBrief descriptionFor more information,
see CommandLine
ThemeTheme to use for UI elements (see examples)-uipalette
Dialogs fontThe font used in the dialogs-dialogfont
HiDPI modeScale the UI by a factor of two when enabled-hidpi
Dialogs positionPosition of dialogs with Stella window-dialogpos
Center windowsAttempt to center application windows, else position at last position-center
List input delayMaximum delay between keypresses in filelist-widgets before a search string resets. -listdelay
Mouse wheel scrollNumber of lines a mouse scroll will move in list-widgets-mwheel
Double-click speedSpeed of mouse double-clicks-mdouble
Controller repeat delayDelay before controller input repeats-ctrldelay
Controller repeat rateRate of controller input repeats-ctrlrate

This tab is described in further detail in Advanced Configuration - ROM Launcher.

Snapshot Settings dialog:

ItemBrief descriptionFor more information,
see CommandLine
Save pathSpecifies where to save snapshots-snapsavedir
Continuous snapshot intervalInterval (in seconds) between snapshots-ssinterval
Use actual ROM nameUse the actual ROM filename instead of the internal database name-snapname
Overwrite existing filesWhether to overwrite old snapshots-sssingle
Create pixel-exact image (no zoom/post-processing)Save snapshot using the exact pixels from the TIA image, without zoom or any post-processing effects-ss1x

Developer Settings dialog:

This tab is described in further detail in Advanced Configuration - Developer Options/Integrated Debugger.

Game Properties dialog:

This dialog allows you to change all ROM properties as described in Advanced Configuration - Game Properties.

Audit ROMs dialog:

This dialog is described in further detail in Advanced Configuration - ROM Audit Mode.

Event Remapping/Input Devices

Almost every event in Stella can be remapped to another key on the keyboard or to buttons on up to eight joysticks/gamepads (see Getting Started - Keyboard Layout for those events which can/cannot be remapped).

Note that there are currently two separate event modes in Stella; emulation mode and user-interface (UI) mode. Each mode has separate mappings, so (for example) while in emulation mode, the left arrow could mean 'joystick 0 left', while in UI mode it could mean 'move cursor left'. Emulation mode occurs whenever you're actually playing a game. UI mode occurs whenever a user interface is present (ROM launcher, debugger, settings menu, etc.). Because of these different modes, there are two separate mapping areas.

To remap an event:

  1. Enter Options Menu and click the Input Settings button.
  2. If you wish to remap emulation events, click the 'Emulation Events' tab. Here you can also filter for the type of events. Otherwise, click the 'UI Events' tab for user interface events.
  3. Select event you want to remap and click the 'Map' button.
  4. Now define the input:
    • Either press a key, a modifier key (Control, Shift...) or a modifier+key combination.
    • Or use a controller direction, a button or a button+controller direction combination.
    Then that key (combination) or controller action will be bound to the selected event.
    • If nothing seems to happen, either Stella can't see the input device, or the selected event doesn't support being remapped to the input device.
    • The same input can be used for multiple controller types (e.g. 'Right' for 'P0 Joystick Right' and 'Paddle 0 Turn Right').
    • If the same input is used again for the same controller type, the old mapping will be removed.
    • Events which are available in both event modes can be remapped individually.
    • Left and right modifiers are mapped separately when used alone.
You can also:

The following screenshots illustrate the event remapping process:

Finally there is a 'Combo' button in the 'Emulation Events' tab, accessible only when a Combo event has been selected from the list of events on the left. Clicking 'Combo' will show a dialog similar to the following:

In this dialog, you can assign various events to the selected combo event. Note that this simply assigns multiple events to the combo; you still need to map the combo event itself to some action, as described in the 'remap an event' section above.

Device and port settings can be configured under the 'Devices & Ports' tab, shown below:

ItemBrief descriptionFor more information,
see CommandLine
Joystick deadzone sizeDeadzone area for axes on joysticks/gamepads-joydeadzone
(Analog paddle) SensitivitySensitivity of an analog paddle-psense
Analog paddle) Dejitter averagingStrength of paddle input averaging, suppresses mouse jitter-dejitter.base
(Analog paddle) Dejitter reactionStrength of paddle reaction to fast paddle movements, suppresses mouse jitter-dejitter.diff
Digital paddle sensitivitySensitivity used when emulating a paddle using a digital device-dsense
Allow all 4 directions ...Allow all 4 joystick directions to be pressed simultaneously-joyallow4
Use modifier key combosEnable using modifier keys in keyboard actions-modcombo
Swap Stelladaptor portsSwap the order of the detected Stelladaptors/2600-daptors (see Advanced Configuration - Stelladaptor/2600-daptor Support)-saport
Joystick databaseShow all joysticks that Stella knows about, with the option to remove them 
Erase EEPROMErase the whole AtariVox/SaveKey flash memory 
AVox serial portDescribed in further detail in Advanced Configuration - AtariVox/SaveKey Support -avoxport

Mouse settings can be configured under the 'Mouse' tab, shown below:

ItemBrief descriptionFor more information,
see CommandLine
Use mouse as ...Allow the mouse to emulate various controllers-usemouse
(Sensitivity) PaddleSensitivity used when emulating a paddle using a mouse-msense
(Sensitivity) TrackballSensitivity used when emulating a trackball device using a mouse-tsense
(Sensitivity) Driving controllerSensitivity used when emulating a driving controller device using a mouse-dcsense
Mouse cursor visibilityShow/hide cursor depending on current state-cursor
Grab mouse ...Keep mouse in window in emulation mode
(only when used as controller)
Note: The sensitivity may greatly vary when the mouse is not grabbed.

ROM Launcher

Several options are configurable in the ROM launcher. The size of the launcher and fonts, as well as the 'ROM Info Viewer' can be changed in UI Settings - Launcher dialog, as shown below:

Most of the options are self-explanatory, except for the 'ROM info width', which is described below.

ROM Info Viewer

Stella supports viewing snapshots and ROM properties of the currently selected ROM in the ROM launcher. Support is automatic, as long as your snapshot directory contains snapshots in the appropriate format. An archive of updated snapshots will be available on the Stella webpage. This archive may be updated periodically as new ROMs are found, and also for each new release of Stella. Note that the snapshots can be any size generated by Stella; they will be resized accordingly.

The ROM Info Viewer's width can be defined between 0% (off) and 100%. The value is relative to the launcher width. For too small or too large values, Stella will automatically correct the width at runtime so that the ROM names and the current ROM's information always have enough space.

The following snapshots illustrate the various font sizes and rom info widths:

ROM Info Viewer width at 40%, UI sized 800x480, small launcher font:

ROM Info Viewer width at 32%, UI sized 1000x720, medium launcher font:

ROM Info Viewer width at 50% , UI sized 1280x900, large launcher font:

The text box in the upper right corner can be used to narrow down the results in the ROM listing. When this box is empty, all files are shown (subject to the restrictions from the filtering option, explained below). Typing characters here will show only those files that match that pattern. For example, typing 'Activision' will show only files that contain the word 'Activision' in their name. This is very useful for quickly finding a group of related ROMs. Note that the search is not case sensitive, so you don't need to worry about capital or lower-case letters.

ROM Launcher Context Menu

The ROM launcher also contains a context menu, selected by clicking the right mouse button anywhere in the current window. This context menu contains the following items:

  1. Power-on options: Selecting this option shows a dialog whereby ROM properties can be temporarily overridden, and joystick/console buttons can be temporarily held down. Selecting options from this dialog will cause all ROMs launched after that to use those properties you specify. Clicking Defaults will disable its functionality, and use ROM properties as defined by the ROM itself. The dialog is as follows (see Advanced Configuration - Game Properties for more information concerning ROM properties):

    ItemFor more information,
    see Commandline
    Bankswitch type-bs
    TV type-tv
    Left difficulty-ld
    Right difficulty-rd
    Startup mode-debug
    Left joy items-holdjoy0
    Right joy items-holdjoy1
    Console: Select-holdselect
    Console: Reset-holdreset

  2. Show only ROM files: Selecting this reloads the current listing, showing only files that have a valid ROM extension.

  3. Show all files: Selecting this reloads the current listing, showing all files (with no restriction on file name).

  4. Reload listing: Selecting this performs a reload of the current listing. It is an alternative to pressing the Control-r key combo.

ROM Audit Mode

Stella has the ability to rename all your ROMs according to the name specified in the properties database. This is useful if you've downloaded ROMs in DOS 8.3 naming format, and wish the filenames to be more descriptive, or the current filenames are too large to see in the launcher.

This feature is accessible from Options => Audit ROMs, and is only available while in ROM launcher mode. The dialog box for this feature is as follows:

Simply select the ROM path with the 'Audit path' button, and click the 'Audit' button. The ROMs will then be renamed according to their internal properties. When the operation is complete, the number of ROMs that were renamed (as well as ones that weren't) will be shown.

There are several items to take note of:

Stelladaptor/2600-daptor Support

Stella supports real Atari 2600 joysticks, paddles, driving controllers and trackballs (CX22/CX80 'Trak-Ball', Atari and Amiga mouse) using the Stelladaptor and 2600-daptor devices.

Stella can use up to two adaptors; any extra ones are ignored. Stelladaptor devices will be automatically detected and configured. The actual controllers can be plugged/unplugged while the emulator is running, although you will need to restart the game currently being emulated.

The detection and configuration is as follows:

AtariVox/SaveKey Support

Stella supports a real AtariVox device for the speech/SpeakJet portion of the controller. You will need a real AtariVox device as well as some means of connecting it to your computer (some sort of serial port/USB adaptor). There should be drivers for your serial convertor, which allow your particular operating system to 'see' the device (configuring this is outside the scope of this document). Once your operating system properly detects the AtariVox, you will need to tell Stella which serial port it is connected to. This is done by using the '-avoxport' commandline argument, or by setting it in the UI under the 'Devices & Ports' tab in Advanced Configuration - Input Devices.

Note that you must use the entire name of the port as specified by your operating system. For example, in Windows this would be COM1, COM2, etc.; Linux and macOS tend to use names similar to '/dev/xxxxxx'. For now, only Linux/UNIX, macOS, and Windows are supported.

Support for the EEPROM portion of the AtariVox and SaveKey is currently emulated. That is, a file will be created on your computer simulating the EEPROM; the actual EEPROM hardware itself will not be accessed or modified. This is very useful in the testing stages of creating a new game, since writing to a real EEPROM many times will eventually wear it out.

The location of EEPROM files will depend on the version of Stella, as follows:

Linux/Unix $HOME/.config/stella/nvram/atarivox_eeprom.dat
Macintosh $HOME/Library/Application Support/Stella/nvram/atarivox_eeprom.dat
$HOME/Library/Application Support/Stella/nvram/savekey_eeprom.dat
Windows %APPDATA%\Stella\nvram\atarivox_eeprom.dat
If using 'basedir'
or 'baseinappdir'

Note that these EEPROM files will be created when necessary, and initialized as a real EEPROM would be (containing all $FF). The files can be manually deleted, which is very useful in testing cases where a ROM is accessing the EEPROM for the first time. You can also reset the EEPROM to a clean state.

Developer Options/Integrated Debugger

Several developer related options can be configured in the 'Developer Settings' dialog. Two sets ('Player settings', 'Developer settings') allow easy adjustment of all settings for different use cases (playing or developing games) at once.

Developer Settings dialog (Emulator)

ItemBrief descriptionFor more information,
see CommandLine
Player/Developer settingsSelects the active settings set-dev.settings
Console info overlayOverlay console info on the TIA image during emulation.-plr.stats
ConsoleSelect the console type, this affects Color/B&W/Pause key emulation and zero-page RAM initialization-plr.console
Random startup bankRandomize the startup bank (only for selected bankswitch types)-plr.bankrandom
Randomize zero-page ...When loading a ROM, randomize all RAM content instead of initializing with all zeroes (for 'Console' = 'Atari 2600' only)-plr.ramrandom
Randomize CPUWhen loading a ROM, randomize the content of the specified CPU registers-plr.cpurandom
Drive unused TIA pins ...Unused TIA pins are read random instead of the last databus values-dev.tiadriven
Break on reads from ... A read from a write port interrupts emulation and the debugger is entered. -dev.rwportbreak
Break on write to ... A write to a read port interrupts emulation and the debugger is entered. -dev.wrportbreak
Fatal ARM emulation ... Thumb ARM emulation throws an exception and enters the debugger on fatal errors -dev.thumb.trapfatal
Display AtariVox...Display a message when the AtariVox/SaveKey EEPROM is read or written-plr.eepromaccess

Developer Settings dialog (TIA):

ItemBrief descriptionFor more information,
see CommandLine
Chip typeType of emulated TIA chip. Allows testing for TIA versions which exhibit timing problems in certain games. The 'Custom' option allows testing for glitch combinations.-dev.tia.type
Inverted HMOVE clock...Emulates the Kool-Aid Man collision and Cosmic Ark stars glitches for the given objects. -dev.tia.plinvphase
Delayed PlayfieldEmulates playfield registers delayed by one color clock. This e.g. causes glitches in Pesco (stray playfield pixel) and Quick Step! (colored step borders) -dev.tia.delaypfbits
Delayed VDEL... swap forEmulates a VDELP0/P1/BL swap delayed by one color clock. This e.g cause glitches in the He-Man title screen. -dev.tia.delayplswap

Developer Settings dialog (Video):

ItemBrief descriptionFor more information,
see CommandLine
Jitter/roll effectEmulate screen roll with inconsistent scanline
(Jitter/roll) RecoveryDetermines recovery time for screen
PAL color-lossUse PAL color-loss effect-plr.colorloss
Debug colorsUse fixed debug colors-plr.debugcolors
Player 0
Missile 0
Player 1
Missile 1
Set color for specific object in 'Debug Colors' mode (PF0, PF1 and PF2 have a slightly different luminance)

Disabled in ROM launcher mode

Developer Settings dialog (Time Machine)

ItemBrief descriptionFor more information,
see CommandLine
Time Machine When the Time Machine is enabled, Stella will automatically buffer save states in the interval described below. The user can then navigate back and forth within the recorded timeline.
Note: This buffer is identical with the one described in Debugger - Global Buttons. It is independent from the save states manually created with F9.
Buffer size Defines the Time Machine buffer size. The larger the buffer, the less save states have to be compressed to reach the horizon.
Uncompressed size (*) Defines the uncompressed Time Machine buffer size. States within this area will not be compressed and keep their initial interval.
Interval Defines the interval between two save states when they are created.
Horizon Defines the horizon of the Time Machine. A large horizon allows going back further in time. To reach the horizon, save states will be compressed (*). This means that more and more intermediate states will be removed and the interval between save states becomes larger the further they are back in time.
(*) Compression only works if 'Uncompressed size' is smaller than 'Buffer size'.

Developer Settings dialog (Debugger)

ItemBrief descriptionFor more information,
see CommandLine
Font sizeSelf-explanatory-dbg.fontsize
Font styleSelf-explanatory-dbg.fontstyle
Debugger width/heightSelf-explanatory-dbg.res
Trap on 'ghost' readsDefines whether the debugger should consider CPU 'ghost' reads for trap addresses.-dbg.ghostreadstrap

Many more options are available for ROM developers, which are described in different sections of this manual, as follows:

Finally, Stella contains an extensive, built-in debugger. Have a look at this page for integrated debugger documentation.

Settings File

Stella will remember when you change a setting either at the command line or while the emulation is running, and use the settings the next time you start the emulator. The settings are saved in a text file which can be edited outside of Stella. This file can contain your default options, and eliminates the need to specify them on the command line. Any options specified on the command line will override those in the settings file.

The syntax for the settings file is very straightforward. Any line starting with a ';' character is considered a comment and is ignored. Other lines must be of the form: command = value, where command is the same as that specified on the command line (without the '-' character), and value is dependent on the command.

For example, the following table illustrates how command line and settings entries are similar:

Command Line Settings File
-video opengl video = opengl
-volume 75 volume = 75
-center 1 center = 1 (or center = true)

The settings file has a special name/location depending on which version of Stella you use, which is not configurable:

Linux/Unix $HOME/.config/stella/stellarc
Macintosh Not applicable; settings are saved in $HOME/Library/Preferences/Stella-emu.plist
Windows %APPDATA%\Stella\stella.ini
If using 'basedir'
or 'baseinappdir'
_BASEDIR_/stellarc (or stella.ini)

Cheatcode Manager

Stella contains support for Bob Colbert's Cheetah cheat codes, as well as an extended Stella-specific type of cheat code that works on bankswitched ROMs.

To add/remove/edit a cheat code, enter the 'Cheat Code' dialog:

Currently, there are three types of cheatcodes available, all of which must be entered in hexadecimal format:

There's also the concept of one shot codes. These codes work exactly the same as above, except they aren't saved. They are evaluated once and immediately discarded.

Here are a few cheat codes we've found:

Pitfall (standard Cheetah codes):
   5b0ea1 - infinite lives
   723ea1 - infinite time
   aa5??0 - set starting level, ?? = 01 to ff (d0 is kinda neat)

Battlezone (Stella extended codes):
   1236ea1 - infinite lives

Ms Pac-Man (Stella extended codes):
   108fea1 - infinite lives

The name of the cheat database file will depend on the version of Stella, as follows:

Linux/Unix $HOME/.config/stella/stella.cht
Macintosh $HOME/Library/Application Support/Stella/stella.cht
Windows %APPDATA%\Stella\stella.cht
If using 'basedir'
or 'baseinappdir'

Stella will require a restart for changes to this file to take effect.

Viewing the System Log

Stella maintains a log of its operations when the program first starts up, and while it is running. In older releases, this information was only viewable from the commandline. However, the current release allows you to see this information from within the UI. This can be selected from the main Options menu, where it is labelled "System Logs". Clicking on the button will show a window similar to the following:

ItemFor more information,
see Commandline
Log level-loglevel
Print to console-logtoconsole

The log levels are self-explanatory (None, Basic, Verbose). The "Print to console" option emulates the behaviour of older versions of Stella, whereby the logged output is also shown on the commandline from which Stella was launched (if it was launched in that fashion). Finally, the current contents of the system log can be saved to your home directory by clicking the "Save log to disk" button.

Game Properties

Stella uses game properties to specify the "best" emulator settings for a game. As of version 2.2 of Stella, a default database of properties are built-in, but you may modify these through the use of a file or within the corresponding Game Properties dialogs. This file will contain all properties modified by the user. So this means that when you upgrade Stella, your personal properties settings are preserved.

Property File

A property file consists of some number of blocks. Each block in the file contains the properties for a single game. For example the general format of a property file is:

   ; Comments
   "Cart.MD5"  "Value"
   "Property"  "Value"

   ; Comments
   "Cart.MD5"  "Value"
   "Property"  "Value"

   . . .

   ; Comments
   "Cart.MD5"  "Value"
   "Property"  "Value"

Every block in the property file must have a unique value for the Cart.MD5 property.


Each block in a property file consists of a set of properties for a single game. Stella supports the properties described below:

Cart.Type: Indicates the bank-switching type for the game. The value of this property must be either Auto or one of the following (for more information about bank-switching see Kevin Horton's 2600 bankswitching document or the documentation in each cartridge's source code file) types. Types marked as (¹) do currently have no reliable auto-detection, those marked as (²) are not fully supported in the debugger:
 Type DescriptionFile Extension
(to force type)
0840 8K ECONObanking .084, .0840
2IN1 ¹4-32K Multicart (2 games) .2N1
4IN1 ¹8-32K Multicart (4 games) .4N1
8IN1 ¹16-64K Multicart (8 games) .8N1
16IN1 ¹32-128K Multicart (16 games) .16N, .16N1
32IN1 ¹64-128K Multicart (32 games) .32N, .32N1
64IN1 ¹64/128K Multicart .64N, .64N1
128IN1 ¹256/512K Multicart .128, .128N1
2K 32-2048 bytes Atari .2K
3E 512K Tigervision + 32K RAM.3E
3EX 512K Tigervision + 256K RAM.3EX
3E+ 3E+ (TJ modified 3E) .3EP, .3E+
3F 512K Tigervision .3F
4A50 ²64K 4A50 + RAM .4A5, .4A50
4K 4K Atari .4K
AR ²Supercharger .AR
BUS Experimental.BUS
CDF Chris, Darrell, Fred (includes CDFJ).CDF
CM ¹Spectravideo CompuMate .CM
CTY ²CDW - Chetiry .CTY
CV CommaVid extra RAM .CV
DPC Pitfall II .DPC
DPC+Enhanced DPC .DPP, .DPC+
E0 8K Parker Bros .E0
E7 16K M-network .E7
E78K 8K M-network .E78, .E78K
EF 64K Homestar Runner .EF
EFSC 64K Homestar Runner + RAM.EFS, .EFSC
F0 Dynacom Megaboy .F0
F4 32K Atari .F4
F4SC 32K Atari + RAM .F4S, .F4SC
F6 16K Atari .F6
F6SC 16K Atari + RAM .F6S, .F6SC
F8 8K Atari .F8
F8SC 8K Atari + RAM .F8S, .F8SC
FA2 CBS RAM Plus 24/28K .FA2
FC Amiga Power Play Aracde 16/32K .FC
FE 8K Decathlon .FE
MDM Menu Driven Megacart .MDM
SB 128-256K SUPERbanking .SB
TVBOY512K TV Boy (127 games).TVB, .TVBOY
UA 8K UA Ltd. .UA
UASW 8K UA Ltd. (swapped banks).UASW
WD Wickstead Design (Pink Panther) .WD
WDSW Wickstead Design (Pink Panther) (bad).WDSW
X07 ¹64K AtariAge .X07
Cart.StartBank: Indicates which bank to use for reading the reset vector.
Display.Format: Indicates the television format the game was designed for. The value must be Auto or one of the following. Types marked as (¹) do currently have no reliable auto-detection. A format can be enforced by using one of the following pattern in the filename.
 Format Filename Pattern (to force format)
NTSC50 ¹NTSC50, NTSC 50, NTSC-50
PAL60 ¹PAL60, PAL 60, PAL-60
Display.VCenter: Indicates the offset for the vertical center of the display. The value must be n such that -20 <= n <= 20.
Display.Phosphor: Indicates whether the phosphor effect should be emulated or not. The value must be Yes or No.
Display.PPBlend: Indicates the amount of blending which will occur while using the phosphor effect. The value must be n such that 0 <= n <= 100. The default value is whatever is specified for tv.phosblend.
Cart.Sound: Indicates if the game should use 1 or 2 channels for sound output. All original Atari 2600 machines supported 1 channel only, but some homebrew games have been written to take advantage of stereo sound mods. The value must be Mono or Stereo.

Console.TVType: Indicates the default television setting for the game. The value must be Color or BW.
Console.LeftDiff: Indicates the default difficulty setting for the left player. The value must be A or B.
Console.RightDiff: Indicates the default difficulty setting for the right player. The value must be A or B.

Indicates what type of controller the left and right player uses. The value must be either Auto or one of the following types. Types marked as (¹) do not have auto-detection yet.
 Type Description
JoystickAtari's famous black joystick that was originally included with the system.
BoosterGrip ¹A controller add-in that plugs directly into the joystick port and provides a pass-through for the joystick. In doing so, it provides the two independent buttons.
Paddles Standard paddle controllers for use with games such as Breakout and Warlords. One pair of controller per connector (allows for 4-player Warlords).
Paddles_IAxis ¹Same as Paddles, except the axes are inverted.
Paddles_IAxDr ¹Same as Paddles, except both the axes and direction of movement are inverted.
Driving ¹ Looks like a paddle, but allows 360 movement. Only one unit per connector, unlike paddles which were sold in pairs.
KeyboardAlso known as the Star Raiders controller, functionally identical to the Kid's Controller and Keyboard Controller. Game included an overlay with commands, for use with Star Raiders.
AmigaMouseCommodore Amiga computer mouse.
AtariMouseAtari ST computer mouse.
TrakballStandard Atari 2600 CX22/CX80 'Trak-Ball' controller.
AtariVox ¹A SpeakJet based unlimited-vocabulary speech/sound synthesizer with 32K EEPROM.
SaveKeyA 32K EEPROM for saving high scores, etc. (the EEPROM portion of an AtariVox).
Genesis Sega Genesis controller, which can be used similar to a BoosterGrip, giving an extra button.
CompuMate ¹Spectravideo CompuMate (if either left or right is set, CompuMate is used for both).
LightgunAtari XG-1 compatible Light Gun
Mindlink ¹Mindlink controller.
KidVid ¹KidVid controller, limitted suport (8, 9 and 0 start the games).
Console.SwapPorts: Indicates that the left and right ports should be swapped internally. This is used for ROMs like 'Raiders of the Lost Ark' where the Player 0 joystick is plugged into the right joystick port. The value must be Yes or No.
Controller.SwapPaddles: Indicates that the left and right paddles in a particular port should be swapped. This is used for ROMs like 'Demons to Diamonds' where the default paddle is paddle 1, not paddle 0. Other ROMs such as 'Tac-Scan' default to paddle 3, which can be set using both 'Controller.SwapPaddles' and 'Console.SwapPorts'. The value must be Yes or No.
Controller.PaddlesXCenter: Defines the horizontal center of the paddles (range -10..30).
Controller.PaddlesYCenter: Defines the vertical center of the paddles (range -10..30).
Controller.MouseAxis: Indicates how the mouse should emulate virtual controllers. In 'Auto' mode, the system decides how to best use the mouse. Otherwise, XY indicates how to use the X/Y axis (ie, 02 is paddle0/paddle2). Currently, the mouse X-axis and left button are tied together, as are the Y-axis and right button. The value must be Auto or XY, as follows:
 Id Controller
0 Paddle 0
1 Paddle 1
2 Paddle 2
3 Paddle 3
4 Driving 0
5 Driving 1
6 MindLink 0
7 MindLink 1
An optional second parameter (default of 100) indicates how much of the paddle range that the mouse should emulate.

Cart.Name: Indicates the actual name of the game. When you save snapshots, load/save state files, or use the ROM Audit Mode functionality, this is the name that will be used for the respective file(s).
Cart.MD5: Indicates the MD5 checksum of the ROM image as a string of hexadecimal digits. Stella uses this property while attempting to match a game with its block of properties. If the value of the property matches the MD5 checksum of the ROM image then Stella uses that block of properties for the game. You can use the GNU md5sum program, which is included with most Linux distributions, to calculate the MD5 checksum of a ROM image.
Cart.Manufacturer: Indicates the game's manufacturer.
Cart.ModelNo: Indicates the manufacturer's model number for the game.
Cart.Rarity: Indicates how rare a cartridge is, based on the scale described on AtariAge.
Cart.Note: Contains any special notes about playing the game.

The buttons at the bottom of the dialogs work as follows:

The name of the properties file will depend on the version of Stella, as follows:

Linux/Unix $HOME/.config/stella/
Macintosh $HOME/Library/Application Support/Stella/
Windows %APPDATA%\Stella\
If using 'basedir'
or 'baseinappdir'

Note: For manual changes to the property files Stella will require a restart to take effect.

Palette Support

An Atari 2600 palette consists of 128 colours, which are different for the three major television standards (NTSC, PAL, SECAM). Stella supports two built-in palettes and one user-defined palette for each format. These are set using the '-palette' option, and are described as follows:

standard The default palette from Stella 1.4 onwards.
z26 The palette from the z26 emulator.
user An external palette file, supplied by the user.
custom A palette generate from user-defined phase shift.

A user-defined palette has certain restrictions, further described as follows:

The name of the palette file will depend on the version of Stella, as follows:

Linux/Unix $HOME/.config/stella/stella.pal
Macintosh %HOME/Library/Application Support/Stella/stella.pal
Windows %APPDATA%\Stella\stella.pal
If using 'basedir'
or 'baseinappdir'

Note that to actually use the external palette, the palette file must exist and be valid, and the palette option should be set to user (in Video Settings dialog). The current ROM will have to be reloaded for changes to this file to take effect.


Bradford W. Mott started developing Stella during the fall of 1995, and Stephen Anthony has maintained the project since around 2004. Over the years, a number of people from around the world have contributed to the project. Some people have provided technical help while others have offered suggestions and praise. The Stella Team is grateful for all the help and support it has received over the years. A (likely incomplete) list of the people who have played a part in bringing Stella to you is available on the main Stella webpage Credits List. If we've missed someone, please let us know.

License and Disclaimer


Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.


The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.


0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

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In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

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The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

5. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

7. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.