A multi-platform Atari 2600 VCS emulator

Release 3.9.3

User's Guide

  1. A Brief History of the Atari 2600
  2. Introduction
  3. Getting Started
  4. Advanced Configuration
  5. Acknowledgments
  6. License and Disclaimer

February 1999 - January 2014
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

1. Requirements

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 XP/Vista/7 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, MacOSX and Windows. The Stella Team is interested in hearing about any problems you may encounter with diverse operating systems and CPU types.

2. Installation

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.




3. 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 is illegal to use ROM images of games that you do not actually own since these games are still 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).

4. 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 will be asked to select the default ROM directory to use. This is where you have all your ROMs, collected as described in the previous section. Several dialogs will be shown, similar to the following:


The browser should be self-explanatory. The 'Go Up' button moves to the parent folder (if it exists), and the 'Base Dir' button moves to the base directory where, by default, all Stella-related files are stored. Double-clicking an item will enter that directory. Click 'Choose' to select the location, or 'Cancel' to exit the browser. Note that if you don't select a ROM directory now, you will be prompted again the next time Stella is started.

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

Once you've correctly set the default ROM directory, 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). 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.

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. 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).

5. 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.

Console Controls (can be remapped)

Function Key (Standard) Key (MacOSX)
Exit emulator Control + q Cmd + q
Exit game mode/enter launcher mode Escape Escape
Enter/exit options mode Tab Tab
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
Change current state slot F10 F10
Load state from current slot F11 F11
Save PNG snapshot F12 F12
Pause/resume emulation Pause  

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 Space
Trigger Button 4
Booster Button 5
Function Key
Joystick Up Y
Joystick Down H
Joystick Left G
Joystick Right J
Fire Button F
Trigger Button 6
Booster Button 7

Paddle Controller digital emulation (can be remapped independently of joystick controller)

Left Paddles Right Paddles
Function Key
Paddle 0 decrease Same as 'Joy0 Left'
Paddle 0 increase Same as 'Joy0 Right'
Paddle 0 Fire Same as 'Joy0 Fire'
Paddle 1 decrease Same as 'Joy0 Up'
Paddle 1 increase Same as 'Joy0 Down'
Paddle 1 Fire Same as 'Joy0 Booster'
Function Key
Paddle 2 decrease Same as 'Joy1 Left'
Paddle 2 increase Same as 'Joy1 Right'
Paddle 2 Fire Same as 'Joy1 Fire'
Paddle 3 decrease Same as 'Joy1 Up'
Paddle 3 increase Same as 'Joy1 Down'
Paddle 3 Fire Same as 'Joy1 Booster'

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'

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 Booster'
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 Booster'

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 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

TV effects (only active in TIA mode when using OpenGL rendering)

Function Key (Standard) Key (MacOSX)
Disable TV effects Alt + 1 Cmd + 1
Select 'Composite' preset Alt + 2 Cmd + 2
Select 'S-video' preset Alt + 3 Cmd + 3
Select 'RGB' preset Alt + 4 Cmd + 4
Select 'Badly adjusted' preset Alt + 5 Cmd + 5
Select 'Custom' preset Alt + 6 Cmd + 6
Decrease scanline intensity Shift-Alt + 7 Shift-Cmd + 7
Increase scanline intensity Alt + 7 Cmd + 7
Disable scanline interpolation Shift-Alt + 8 Shift-Cmd + 8
Enable scanline interpolation Alt + 8 Cmd + 8
Select previous 'Custom' mode attribute (*) Shift-Alt + 9 Shift-Cmd + 9
Select next 'Custom' mode attribute (*) Alt + 9 Cmd + 9
Decrease 'Custom' selected attribute value (*) Shift-Alt + 0 Shift-Cmd + 0
Increase 'Custom' selected attribute value (*) Alt + 0 Cmd + 0
Items marked as (*) are only available in 'Custom' preset mode

Developer Keys in TIA mode (cannot be remapped)

Function Key (Standard) Key (MacOSX)
Set "Display.YStart" to next larger value Alt + PageUp Cmd + PageUp
Set "Display.YStart" to next smaller value Alt + PageDown Cmd + PageDown
Set "Display.Height" to next larger value Control + PageUp Control + PageUp
Set "Display.Height" to next smaller value Control + PageDown Control + PageDown
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 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 TIA HMOVE blanks Alt + m Cmd + m
Toggle TIA 'Fixed Debug Colors' mode Alt + Comma Cmd + Comma
Toggle all TIA objects Alt + . Cmd + .
Toggle all TIA collisions Shift-Alt + . Shift-Cmd + .

Other Keys (cannot be remapped, except those marked with '*')

Function Key (Standard) Key (MacOSX)
Switch to next larger zoom level Alt + = Cmd + =
Switch to next smaller zoom level Alt + - Cmd + -
Toggle fullscreen/windowed mode Alt + Enter Cmd + Enter
Decrease volume (*) Alt + [ Cmd + [
Increase volume (*) Alt + ] Cmd + ]
Toggle console type in increasing order (NTSC/PAL/SECAM, etc)) Control + f Control + f
Toggle console type in decreasing order (NTSC/PAL/SECAM, etc)) Shift-Control + f Shift-Control + f
Save current properties to a new properties file Control + s Control + s
Switch mouse between controller emulation modes Control + 0 Control + 0
Swap Stelladaptor/2600-daptor port ordering Control + 1 Control + 1
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
Toggle 'phosphor' effect Alt + p Cmd + p
Toggle palette Control + p Control + p
Toggle PAL color-loss effect Control + l Control + l
Save continuous PNG snapshots Alt + s Cmd + s

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)

6. 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)
Mindlink ✓ (axis ignored)
AtariVox N/A N/A N/A N/A N/A
SaveKey N/A N/A N/A N/A N/A

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.

1. 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 <soft|gl>
Use software or OpenGL rendering mode.
-gl_lib <filename>
OpenGL mode only. Specify the OpenGL library to use (only use this if you know what you're doing). For MacOSX, this should probably be left blank.
-gl_inter <1|0>
OpenGL mode only. Use interpolation for the TIA image (results in blending/smoothing of the image).
-gl_aspectn <number>
-gl_aspectp <number>
OpenGL mode only. Specify the amount (as a percentage) to scale the TIA image width in NTSC and PAL mode. Since many video modes do not use square pixels, you can reduce width until the pixels appear square. Allowable values are 80 - 120; I find 85 - 90 gives the most authentic look for NTSC, and 105 - 110 for PAL.
-gl_fsscale <1|0>
OpenGL mode only. Stretch TIA image completely while in fullscreen mode (vs. an integral stretch which won't necessarily completely fill the screen).
-gl_vbo <1|0>
OpenGL mode only. Use the Vertex Buffer Object extension, if available. This is enabled by default.
-gl_vsync <1|0>
OpenGL mode only. Synchronize screen updates to the vertical blank period. This can result in smoother updates, and eliminate tearing.
-tv_filter <1 - 6>
OpenGL mode only. Blargg TV effects, 0 is disabled, next numbers in sequence represent presets for 'composite', 's-video', 'RGB', 'bad adjust', and 'custom' modes.
-tv_scanlines <0 - 100>
OpenGL mode only. Blargg TV effects scanline intensity, where 0 means completely off.
-tv_scaninter <1|0>
OpenGL mode only. Blargg TV effects scanline interpolation, resulting in blending/smoothing of the scanlines.
-tv_contrast <number>
OpenGL mode only. Blargg TV effects 'contrast' (only available in custom mode, range -1.0 to 1.0).
-tv_brightness <number>
OpenGL mode only. Blargg TV effects 'brightness' (only available in custom mode, range -1.0 to 1.0).
-tv_hue <number>
OpenGL mode only. Blargg TV effects 'hue' (only available in custom mode, range -1.0 to 1.0).
-tv_saturation <number>
OpenGL mode only. Blargg TV effects 'saturation' (only available in custom mode, range -1.0 to 1.0).
-tv_gamma <number>
OpenGL mode only. Blargg TV effects 'gamma' (only available in custom mode, range -1.0 to 1.0).
-tv_sharpness <number>
OpenGL mode only. Blargg TV effects 'sharpness' (only available in custom mode, range -1.0 to 1.0).
-tv_resolution <number>
OpenGL mode only. Blargg TV effects 'resolution' (only available in custom mode, range -1.0 to 1.0).
-tv_artifacts <number>
OpenGL mode only. Blargg TV effects 'artifacts' (only available in custom mode, range -1.0 to 1.0).
-tv_fringing <number>
OpenGL mode only. Blargg TV effects 'fringing' (only available in custom mode, range -1.0 to 1.0).
-tv_bleed <number>
OpenGL mode only. Blargg TV effects 'bleed' (only available in custom mode, range -1.0 to 1.0).
-tia_filter <filter>
Use the specified filter while in TIA/emulation mode. Currently, this can be zoomZx, where Z={2..10}.
-fullscreen <1|0|-1>
Play the game in fullscreen mode (1 or 0), or completely disable fullscreen mode (-1).
-fullres <auto|WxH>
Use the given resolution in fullscreen mode. If 'auto', let Stella decide which resolution to use.
-center <1|0>
Centers game window (if possible).
-palette <standard|z26|user>
Set the palette to either normal Stella, the one used in the z26 emulator, or a user-defined palette.
-colorloss <1|0>
Enable/disable the PAL color-loss effect.
-framerate <number>
Display the given number of frames per second. Normally, Stella will determine framerate based on number of scanlines. Setting this to 0 automatically enables auto-frame calculation (ie, framerate based on scanlines).
-timing <sleep|busy>
Determines type of wait to perform between processing frames. Sleep will release the CPU as much as possible, and is the preferred method on laptops (and other low-powered devices) and when using GL VSync. Busy will emulate z26 busy-wait behaviour, and use all possible CPU time, but may eliminate graphical 'tearing' in software mode.
-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.
-sound <1|0>
Enable or disable sound generation.
-fragsize <number>
Specify the sound fragment size to use. Linux/Mac seems to work with 512, Windows may need 2048 (but newer versions work with 512 as well).
-freq <number>
Set sound sample output frequency (11025,22050,31400,44100,48000) Default is 31400. Do not change unless you experience sound issues.
-volume <number>
Set the volume (0 - 100).
-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 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.
-joyallow4 <1|0>
Allow all 4 directions on a joystick to be pressed simultaneously. Bumper Bash ignores this setting, and always allows all 4 directions.
-grabmouse <1|0>
Keeps the mouse in the game window in emulation mode.
-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).
-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 10, with larger numbers causing faster movement.
-msense <number>
Sensitivity for emulation of paddles when using a mouse. Valid range of values is from 1 to 15, with larger numbers causing faster movement.
-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.
-ctrlcombo <1|0>
Use control-x key combos. This is normally enabled, since the Quit command is tied to 'Control-q'. However, there are times when 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.
-autoslot <1|0>
Automatically switch to the next available save state slot after saving a ROM state file.
-stats <1|0>
Overlay console info on the TIA image during emulation.
-fastscbios <1|0>
Disable Supercharger BIOS progress loading bars.
-snapsavedir <path>
The directory to save snapshot files to.
-snaploaddir <path>
The directory to load snapshot 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).
-launcherres <WxH>
Set the size of the ROM launcher.
-launcherfont <small|medium|large>
Set the size of the font in the ROM launcher.
-launcherexts <allfiles|allroms|LIST>
Specifies which files to show in the ROM launcher ('allfiles' is self-explanatory, 'allroms' is all files with valid rom extensions (currently: a26, bin, rom, gz, zip), 'LIST' is a ':' separated list of valid rom extensions.
-romviewer <0|1|2>
Hide ROM info viewer in ROM launcher mode (0), or use the given zoom level (1 or 2).
-uipalette <1|2>
Used the specified palette for UI elements. This isn't yet complete.
-listdelay <delay>
Set the amount of time to wait between treating successive keypresses as a single word in list widgets (value can range from 300-1000).
-mwheel <lines>
Set the number of lines a mousewheel will scroll in the UI.
-romdir <dir>
Set the directory where the ROM launcher will start.
-statedir <dir>
Set the directory in which to access state files.
-cheatfile <file>
Set the full pathname of the cheatfile database.
-palettefile <file>
Set the full pathname of the user-defined palette file.
-propsfile <file>
Set the full pathname of the ROM properties file.
-nvramdir <dir>
Set the directory in which to access non-volatile (flash/EEPROM) files.
-cfgdir <dir>
Set the directory in which to access Distella config files.
-avoxport <name>
Set the name of the serial port where an AtariVox is connected.
-maxres <WxH>
Useful for developers, this sets the maximum size of window that can be created, allowing to simulate testing on 'smaller' systems.
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 section 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.res <WxH>
Set the size of 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.
-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).
-holdjoy1 <U,D,L,R,F>
Start the emulator with the right joystick direction/button held down (ie, use 'UF' for up and fire).
Start the emulator with the Game Select switch held down.
Start the emulator with the Game Reset switch held down.
-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.
-ramrandom <1|0>
On reset, either randomize all RAM content, or zero it out instead.
-bs <type>
Set "Cartridge.Type" property. See the Game Properties section for valid types.
-type <type>
Same as using -bs.
-channels <Mono|Stereo>
Set "Cartridge.Sound" property.
-ld <A|B>
Set "Console.LeftDifficulty" property.
-rd <A|B>
Set "Console.RightDifficulty" property.
-tv <Color|BW>
Set "Console.TelevisionType" 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.
-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.
-ystart <number>
Set "Display.YStart" property (0 - 64).
-height <number>
Set "Display.Height" property (210 - 256).
-pp <Yes|No>
Set "Display.Phosphor" property.
-ppblend <number>
Set "Display.PPBlend" property, used for phosphor effect (0-100). Default is 77.
-thumb.trapfatal <true|false>
The default of true 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.

2. 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 Settings dialog:

ItemBrief descriptionFor more information,
see CommandLine
Renderer (*)use specified rendering mode (requires restart)-video
TIA Filterfilter for emulation mode -tia_filter
TIA Palettepalette for emulation mode-palette
Fullscrn Resresolution for fullscreen mode-fullres
Timing (*)how to wait between frames (requires restart)-timing
GL FilterOpenGL filter mode-gl_filter
GL Aspect (N)OpenGL width of TIA image in NTSC mode-gl_aspectn
GL Aspect (P)OpenGL width of TIA image in PAL mode-gl_aspectp
Framerateframes per second in emulation mode-framerate
Fullscreen modeself-explanatory-fullscreen
GL FS Stretchstretch fullscreen OpenGL in emulation mode-gl_fsmax
GL VBOenable OpenGL Vertex Buffer Objects-gl_vbo
GL VSyncenable OpenGL vertical synchronization-gl_vsync
PAL color-lossuse PAL color-loss effect-colorloss
Fast SC/AR BIOSskip progress loading bars for SuperCharger ROMs-fastscbios
Show UI messagesoverlay UI messages onscreen-uimessages
Center windowattempt to center application window-center

Video Settings dialog (TV Effects):

ItemBrief descriptionFor more information,
see CommandLine
TV Modedisable TV effects, or select TV preset-tv_filter
Scanline Intensitysets scanline black-level intensity-tv_scanlines
Scanline Interpolationsmooth/blend scanlines into image-tv_scaninter
Adjustable slidersset specific attribute in 'Custom' mode-tv_contrast, tv_hue, etc.
Clone Compositecopy 'Composite' attributes to 'Custom' sliders 
Clone S-Videocopy 'S-Video' attributes to 'Custom' sliders 
Clone RGBcopy 'RGB' attributes to 'Custom' sliders 
Clone Bad Adjustcopy 'Bad Adjust' attributes to 'Custom' sliders 
Revertrevert attribute sliders to saved 'Custom' settings 

Audio Settings dialog:

ItemBrief descriptionFor more information,
see CommandLine
Sample size (*)set size of audio buffers-fragsize
Frequency (*)change sound output frequency-freq
Enable soundself-explanatory-sound

Input Settings dialog:

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

UI Settings dialog (3 tabs):

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

ItemBrief descriptionFor more information,
see CommandLine
Debugger Width/Heightself-explanatory (requires ROM reload)-dbg.res
Set window size for ...self-explanatory presets (requires ROM reload)N/A
Font Styleself-explanatory (requires ROM reload)-dbg.fontstyle

ItemBrief descriptionFor more information,
see CommandLine
Interface Palettepalette to use for UI elements-uipalette
List quick delaytime to wait between keypresses in listwidget-listdelay
Mouse wheel scrollnumber of lines mouse scroll will move in listwidget-mscroll

Snapshot Settings dialog:

ItemBrief descriptionFor more information,
see CommandLine
Save pathspecifies where to save snapshots-snapsavedir
Load pathspecifies where to load snapshots-snaploaddir
Save snapshots according tospecifies how to name saved snapshots-snapname
Continuous snapshot intervalinterval (in seconds) between snapshot-ssinterval
Overwrite existing fileswhether to overwrite old snapshots-sssingle
Disable image filtering (1x mode)save snapshot in 1x mode, without filtering-ss1x

Config Paths dialog:

ItemBrief descriptionFor more information,
see CommandLine
Rom pathspecifies location of ROM files-romdir
Cheat filespecifies location of cheatfile database-cheatfile
Palette filespecifies location of user palette-palettefile
Properties file specifies location of external database-propsfile
State pathspecifies location of state files-statedir
NVRAM pathspecifies location of NVRAM (flash/EEPROM) files-nvramdir

Audit ROMs dialog:

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

Game Properties dialog:

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

3. 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 'Emul. Events' tab. Otherwise, click the 'UI Events' tab for user interface events.
  3. Select event you want to remap and click the 'Map' button.
  4. Press a key or a joystick button, and that key/button 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.
  5. Cancel a remap in progress by clicking 'Cancel', erase a mapping by clicking 'Erase', or reset to default mapping by clicking 'Reset'
  6. Reset to default all mappings by clicking 'Defaults'.

The following screenshots illustrate the event remapping process:

There is also a 'Combo' button in the 'Emulation Events' tab, accessible 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
Stelladaptor port orderSpecifies which virtual port each Stelladaptor/2600-daptor uses (See Advanced Configuration - Stelladaptor/2600-daptor Support)-saport
Use mouse as ...Allow the mouse to emulate various controllers-usemouse
AVox serial portDescribed in further detail in Advanced Configuration - AtariVox/SaveKey Support -avoxport
Joy deadzone sizeDeadzone area for axes on joysticks/gamepads-joydeadzone
Digital paddle sensitivitySensitivity used when emulating a paddle using a digital device-dsense
Mouse paddle sensitivitySensitivity used when emulating a paddle using a mouse-msense
Allow all 4 ...Allow all 4 joystick directions to be pressed simultaneously-joyallow4
Grab mouse ...Keep mouse in window in emulation mode-grabmouse

4. 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 viewer', which is described below.

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.

Currently, there are several restrictions for this feature:

  1. The ROM info viewer can be shown in 1x or 2x mode only.
  2. To view snapshots in 1x mode, the ROM launcher window must be sized at least 640x480. If the launcher isn't large enough, the functionality will be disabled.
  3. To view snapshots in 2x mode, the ROM launcher window must be sized at least 1000x760. If the launcher isn't large enough, an attempt will be made to use 1x mode.

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

ROM info viewer in 1x mode, UI sized 800x480, small launcher font:

ROM info viewer in 1x mode, UI sized 1000x760, medium launcher font:

ROM info viewer in 2x mode, UI sized 1400x900, 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.

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
    Left Difficulty-ld
    Right Difficulty-rd
    TV Type-tv
    Startup Mode-debug
    Left joy items-holdjoy0
    Right joy items-holdjoy1
    Console: Select-holdselect
    Console: Reset-holdreset

  2. Filter listing: Selecting this option shows a dialog whereby one can filter the types of files shown in the listing. The dialog is as follows:

    Currently, the choices are as follows:

    • All files - self explanatory, show all files in the ROM listing. This is the default, and emulates the behaviour of all previous versions of Stella.
    • All roms - show only files with a valid ROM extension. Currently, this means extensions .a26, .bin, .rom, .gz, .zip.
    • ROMs ending with - show only files with a ROM extension as selected from the checkboxes.

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

5. 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:

6. Stelladaptor/2600-daptor Support

Stella supports real Atari 2600 joysticks, paddles and driving controllers using the Stelladaptor and 2600-adaptor devices.

Stella can use up to two adaptors; any extra ones are ignored. Stelladaptor devices will be automatically detected and configured. Stelladaptor devices must be plugged in before starting the application; 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:

7. AtariVox/SaveKey Support

Stella supports a real AtariVox device for the speech/SpeakJet portion of the controller. You will need a real AtariVox device, located here, 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 MacOSX tend to use names similar to '/dev/xxxxxx'. For now, only Linux/UNIX, MacOSX, 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 the EEPROM files are configurable through the '-nvramdir' commandline argument and within the application itself (see Advanced Configuration - Config Paths). If the path for these files hasn't been set, the default location will depend on the version of Stella, as follows:

Linux/Unix ~/.stella/nvram/atarivox_eeprom.dat
Macintosh ~/Library/Application Support/Stella/nvram/atarivox_eeprom.dat
~/Library/Application Support/Stella/nvram/savekey_eeprom.dat
Windows %APPDATA%\Stella\nvram\atarivox_eeprom.dat
(if a file named 'basedir.txt' exists in the application directory containing the full pathname for _BASEDIR_)

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.

8. Developer Options/Integrated Debugger

Many 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.

9. 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 gl video = gl
-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 currently not configurable:

Linux/Unix $HOME/.stella/stellarc
Macintosh Not applicable; settings are saved in ~/Library/Preferences/net.sourceforge.Stella.plist
Windows %APPDATA%\Stella\stella.ini    OR
_BASEDIR_\stella.ini    (if a file named 'basedir.txt' exists in the application directory containing the full pathname for _BASEDIR_)

10. 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 hexidecimal 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 is configurable through the '-cheatfile' commandline argument and within the application itself (see Advanced Configuration - Config Paths). If the path for this file hasn't been set, the default filename will depend on the version of Stella, as follows:

Linux/Unix $HOME/.stella/stella.cht
Macintosh ~/Library/Application Support/Stella/stella.cht
Windows %APPDATA%\Stella\stella.cht    OR
_BASEDIR_\stella.cht    (if a file named 'basedir.txt' exists in the application directory containing the full pathname for _BASEDIR_)

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

11. 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.

12. 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. 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
   "Cartridge.MD5"      "Value"
   "Property"           "Value"

   ; Comments
   "Cartridge.MD5"      "Value"
   "Property"           "Value"

   . . .

   ; Comments
   "Cartridge.MD5"      "Value"
   "Property"           "Value"

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


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

Cartridge.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.
Cartridge.Manufacturer: Indicates the game's manufacturer.
Cartridge.ModelNo: Indicates the manufacturer's model number for the game.
Cartridge.Name: Indicates the actual name of the game. When you save snapshots, load/save state files, or use the 'ROM Audit' functionality, this is the name that will be used for the respective file(s).
Cartridge.Note: Contains any special notes about playing the game.
Cartridge.Rarity: Indicates how rare a cartridge is, based on the scale described on AtariAge.
Cartridge.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. The value must be Mono or Stereo.
Cartridge.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 cartridges source code file). Types marked as (¹) do not currently have reliable auto-detection, those marked as (²) are not fully supported in the debugger:
 Type Description
0840 8K ECONObanking
2IN1 ¹4-32K Multicart (2 games)
4IN1 ¹8-32K Multicart (4 games)
8IN1 ¹16-64K Multicart (8 games)
16IN1 ¹32-128K Multicart (16 games)
32IN1 ¹64-128K Multicart (32 games)
2K 64-2048 byte Atari
3E 32K Tigervision
3F 512K Tigervision
4A50 64K 4A50 + ram
4K 4K Atari
4KSC CPUWIZ 4K + ram
AR Supercharger
BFSC CPUWIZ 256K + ram
CM ¹Spectravideo CompuMate
CV Commavid extra ram
DFSC CPUWIZ 128K + ram
DPC Pitfall II
DPC+Enhanced DPC
E0 8K Parker Bros
E7 16K M-network
EF 64K Homestar Runner
EFSC 64K Homestar Runner + ram
F0 Dynacom Megaboy
F4 32K Atari
F4SC 32K Atari + ram
F6 16K Atari
F6SC 16K Atari + ram
F8 8K Atari
F8SC 8K Atari + ram
FA2 CBS RAM Plus 24/28K
FE 8K Decathlon
MC ¹²C. Wilkson Megacart
SB 128-256k SUPERbanking
UA 8K UA Ltd.
X07 ¹64K AtariAge
Console.LeftDifficulty: Indicates the default difficulty setting for the left player. The value must be A or B.
Console.RightDifficulty: Indicates the default difficulty setting for the right player. The value must be A or B.
Console.TelevisionType: Indicates the default television setting for the game. The value must be Color or BW.
Console.SwapPorts: Indicates that the left and right ports should be swapped internally. This is used for ROMs like 'Raiders' where the Player 0 joystick is plugged into the right joystick port. The value must be Yes or No.
Indicates what type of controller the left and right player uses. The value must be one of the following types:
 Type Description
Joystick Atari's famous black joystick that was originally included with the system.
BoosterGrip A 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 Same as Paddles, except the axes are inverted.
Paddles_IDir Same as Paddles, except the direction of movement is inverted.
Paddles_IAxDr Same as Paddles, except both the axes and direction of movement is inverted.
Driving Looks like a paddle, but allows 360' movement. Only one unit per connector, unlike paddles which were sold in pairs.
Keyboard Also 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.
Trackball22 Standard Atari 2600 CX-22 trackball controller.
Trackball80 Atari ST CX-80 trackball controller.
AmigaMouseCommodore Amiga computer mouse.
AtariVoxA 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 Spectravideo CompuMate (if either left or right is set, CompuMate is used for both).
Mindlink Mindlink controller.
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.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
Display.Format: Indicates the television format the game was designed for. The value must be Auto, NTSC, PAL, SECAM, NTSC50, PAL60 or SECAM60.
Display.YStart: Indicates the scan-line to start displaying at. The value must be n such that 0 <= n <= 64.
Display.Height: Indicates the number of scan-lines to display. The value must be n such that 210 <= n <= 256.
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 77.

The name of the properties file is configurable through the '-propsfile' commandline argument and within the application itself (see Advanced Configuration - Config Paths). If the path for this file hasn't been set, the default filename will depend on the version of Stella, as follows:

Linux/Unix $HOME/.stella/
Macintosh ~/Library/Application Support/Stella/
Windows %APPDATA%\Stella\    OR
_BASEDIR_\    (if a file named 'basedir.txt' exists in the application directory containing the full pathname for _BASEDIR_)

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

13. 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.

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

The name of the palette file is configurable through the '-palettefile' commandline argument and within the application itself (see Advanced Configuration - Config Paths). If the path for this file hasn't been set, the default filename will depend on the version of Stella, as follows:

Linux/Unix $HOME/.stella/stella.pal
Macintosh ~/Library/Application Support/Stella/stella.pal
Windows %APPDATA%\Stella\stella.pal    OR
_BASEDIR_\stella.pal    (if a file named 'basedir.txt' exists in the application directory containing the full pathname for _BASEDIR_)

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.


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