1. Introduction
2. What You Will Need
3. Installation
4. Games
5. Starting A Game
6. Changing Options
7. Keyboard Layout
8. Event Remapping / Input Devices
9. ROM Launcher
10. ROM Audit Mode
11. Stelladaptor Support
12. AtariVox/SaveKey Support
13. Developer Options/Integrated Debugger
14. Settings File
15. Cheatcode Manager
16. Game Properties
17. Palette Support
18. Acknowledgments
19. License and Disclaimer

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

1. Introduction

Stella is a freely distributed multi-platform Atari 2600 VCS emulator; originally developed for Linux by Bradford W. Mott. 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).

Features

• High speed emulation using optimized C++ code
• Supports high quality sound emulation using code derived from Ron Fries' TIA Sound Emulation library, including stereo sound support
• Emulates the Atari 2600 Joystick Controllers using your computer's keyboard or joysticks
• Emulates the Atari 2600 Keyboard Controllers using your computer's keyboard
• Emulates the Atari 2600 Paddle Controllers using your computer's mouse, keyboard or joysticks
• Emulates the Atari 2600 Driving Controllers using your computer's keyboard or joysticks
• Emulates the CBS BoosterGrip Controller using your computer's keyboard or joysticks
• Emulates CX-22 / CX-80 style trackballs and Amiga Mouse using your computer's mouse
• Support for real Atari 2600 controllers using the Stelladaptor
• Support for the speech portion of a real AtariVox device connected to your PC using a USB adaptor
• Supports EEPROM emulation for AtariVox and SaveKey controllers
• Supports all known bankswitching schemes (let us know if there's one we missed)
• Supports cartridge autodetection for almost all bankswitching schemes
• Supports Supercharger single-load and multi-load games
• Supports property file for setting the properties associated with games
• Supports the NTSC, PAL, PAL and SECAM television standards in 50Hz and 60Hz mode
• Supports autodetection of display format for 50Hz vs. 60Hz modes
• Supports several "undocumented features" of the TIA graphics chip used by some games
• TIA emulation supports full collision checking
• Built-in extensive debugger
• Emulation of CRT TV systems with OpenGL shaders, including texturing, colour bleed, RF noise, and phosphor burn-off
• Built-in ROM database with information compiled by RomHunter

2. What You Will Need

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

Note that for this version of Stella, you are not required to have a stella.pro file. ROM properties are built in, and defaults will be used whenever necessary.

General (required for all versions of Stella)

• Enough RAM for the OS + 16MB RAM for the emulation; 32MB highly recommended
• 15 bit color minimum; 16 bit color graphics card highly recommended
• SDL version 1.2.10 or greater, latest version highly recommended
• Zlib version 1.2.3 or greater
• CRT emulation effects require OpenGL 2.0 with GLSL (GL shading language) support
• Joysticks or gamepads are highly recommended
• Mouse or Stelladaptor with real paddles required for paddle emulation
• Some ROM images (See AtariAge for more information)

Linux/UNIX

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

• Linux Kernel 2.4.x, Linux Kernel 2.6.x is highly recommended
• i386 or x86_64 class machine, with 32 or 64-bit distribution
• Other architectures (MIPS, PPC, PPC64, etc) have been confirmed to work, but aren't as well tested as i386/x86_64
• GNU C++ compiler version 4.x and the make utility are required for compiling the Stella source code

Macintosh

The Mac version of Stella is designed to work on a Power Macintosh with the following:

• Mac OSX 10.3 or Above
• 500 MHz G4 PPC/Intel processor or above (Stella may work with a G3 processor, but no hardware is available for testing)
• OpenGL capable video card. Software rendering mode is still available, but as of OSX 10.4 is substandard compared to OpenGL.
• Xcode 3.0 is required to compile the Stella source code

Windows

The Windows version of Stella is designed to work on Windows 2000/XP/Vista/7 with the following:

• Pentium class machine required; OpenGL accelerated video card highly recommended
• 64-bit port has been tested on Windows Vista/7 only; it may work on WinXP64 as well, but isn't a priority
• Visual C++ 2008 is required to compile the Stella source code

Other

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 clean in Linux/Unix and Windows (win32/x64), and is expected to be compatible with 64-bit OSX as well. The Stella team is interested in hearing about any problems you may encounter with diverse operating systems and CPU types.

3. 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.

If you have a supported joystick and driver installed and SDL can access the device, you can play games using joysticks.

Currently, sound is supported using SDL. As long as SDL can detect your sound card, Stella will be able to produce sound.

Linux/UNIX

• Binary DEB (stella-release-1_arch.deb)
  1. Install the binary DEB with the following command:

        dpkg -i stella-release-1_arch.deb

• Binary RPM (stella-release-1.arch.rpm)
  1. Install the binary RPM with the following command:

        rpm -Uvh stella-release-1.arch.rpm

• Compressed tarball : building from source code (stella-release-src.tar.gz)
  • Debian-based distributions:
    1. Extract files from the distribution:

          tar zxvf stella-release-src.tar.gz

    2. Change directories to the stella-release directory
    3. Build the executable with the following command:

          dpkg-buildpackage

    4. Install the executable as indicated in the previous section
  • RPM-based distributions:
    1. Extract files from the distribution:

          tar zxvf stella-release-src.tar.gz

    2. Change directories to the stella-release/src/unix directory
    3. Build the executable with the following command:

          rpmbuild -ba stella.spec

    4. Install the executable as indicated in the previous section
  • Generic build:
    1. Extract files from the distribution:

          tar zxvf stella-release-src.tar.gz

    2. Change directories to the stella-release directory
    3. Configure the build with the following command:

          ./configure (--help for list of options)

    4. Build the executable with the following command:

          make

    5. Install the executable with the following command:

          make install

Macintosh

• Binary DMG file (StellaOSXrelease.dmg)
  1. Mount the disk image, then copy the StellaOSXrelease folder to your hard drive.
• Compressed tarball : building from source code (stella-release-src.tar.gz)
  1. Extract files from the distribution using an archiving program that supports gzipped tar files
  2. Open the stella-release/src/macosx/stella.xcodeproj file using Xcode 3.0
  3. Make sure you have the SDL framework installed where Xcode can find it
  4. Build the 'Stella' project
  5. Copy the StellaOSX.app package somewhere on your system

Windows

• Binary EXE installer (stella-release-arch.exe)
  1. Double-click on the installer and follow the onscreen instructions
• Binary ZIP file (stella-release-windows.zip)
  1. Unzip the binary ZIP file using Winzip or Total Commander
  2. Copy the contents of either 32-bit or 64-bit directory somewhere on your system
• Compressed tarball : building from source code (stella-release-src.tar.gz)
  1. Extract files from the distribution using Winzip, Total Commander, or some other archiving program that supports gzipped tar files
  2. Open the stella-release/src/win32/Stella.sln file using Visual C++ 2008
  3. Make sure you have library and header files installed for SDL and zlib for the correct architecture (32-bit, 64-bit or both), and that Visual Studio is properly configured to find them
  4. Build the 'Stella' solution, making sure to correctly select either 'Win32' or 'x64' mode (depending on the version of Windows you have installed)
  5. For installation:
     • Double-click on Create_builds.bat to generate ZIP and EXE files; you must have the 'flip' and 'zip' applications installed on your system. This will generate the EXE and ZIP files, which can be installed as explained above
     OR
     • Manually copy the Stella.exe, SDL.dll and zlibwapi.dll files somewhere on your system (they may be located in the 'Release' or 'x64\Release' directories)

4. Games

Stella allows you to play games using ROM images of cartridges and cassettes.

Cartridges

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:

1. If you're handy with a soldering iron then you can design and build a device that plugs into the printer port of a PC and read the data from the cartridge
2. You can purchase the Atari 2600 Action Packs by Activision and use their ROM images
3. You can search around the internet and find ROM images to download

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

   % 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.

5. Starting A Game

Once Stella is installed and you have some ROM images you're 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'll probably want to set the locations for ROM files, snapshots, and other external paths. These items are accessible by clicking the Options => Config Files buttons. Many other options can be set here, but for now we'll concentrate on Config Files only:

Config Files dialog:

Item Brief description For more information, see Commandline Rom path specifies location of ROM files -romdir State path specifies location of state files -statedir Cheat file specifies location of cheatfile database -cheatfile Palette file specifies location of user palette -palettefile Properties file specifies location of external stella.pro database -propsfile Snapshot path specifies where to load/save snapshots -ssdir EEPROM path specifies location of EEPROM files -eepromdir Multiple snapshots whether to overwrite old snapshots -sssingle Snapshot in 1x mode save snapshot in 1x mode, without filtering -ss1x

If you include the '~' character at the beginning of a path, it will be expanded to your home directory. For Linux/UNIX, this corresponds to your $HOME directory, but for Windows it means your 'My Documents' folder.

Selecting a new path for an item is done by clicking the appropriate button(s) (in this case, 'Rom path' was selected), which will show a browser as follows:

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. Click 'Choose' to select an item, or 'Cancel' to exit the browser.

Once you've changed your settings, 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/Cmd or Space key(s). If a game uses a more complex controller, see Section 7 - Keyboard Layout for more information.

Command Line

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):

-video <soft|gl>

-gl_lib <filename>

-gl_filter <nearest|linear>

-gl_aspectn <number>
-gl_aspectp <number>

-gl_fsmax <1|0>

-gl_vsync <1|0>

-gl_texrect <1|0>

-tv_tex <off|normal|stag>

-tv_bleed <off|low|medium|high>

-tv_noise <off|low|medium|high>

-tv_phos <1|0>

-tia_filter <filter>

-fullscreen <1|0|-1>

-fullres <auto|WxH>

-center <1|0>

-grabmouse <1|0>

-palette <standard|z26|user>

-colorloss <1|0>

-timing <sleep|busy>

-framerate <number>

-sound <1|0>

-fragsize <number>

-freq <number>

-tiafreq <number>

-volume <number>

-clipvol <1|0>

-cheat <code>

-showinfo <1|0>

-joydeadzone <number>

-joyallow4 <1|0>

-pspeed <number>

-sa1 <left|right>

-sa2 <left|right>

-autoslot <1|0>

-audiofirst <1|0>

-fastscbios <1|0>

-ssdir <path>

-sssingle <1|0>

-ss1x <1|0>

-rominfo <rom>

-listrominfo

-uselauncher <1|0>

-launcherres <WxH>

-launcherfont <small|medium|large>

-launcherexts <allfiles|allroms|LIST>

-romviewer <0|1|2>

-uipalette <1|2>

-listdelay <delay>

-mwheel <lines>

-romdir <dir>

-statedir <dir>

-cheatfile <file>

-palettefile <file>

-propsfile <file>

-eepromdir <dir>

-avoxport <name>

-help

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.

-debuggerres <WxH>

-break <address>

-debug

-holdreset

-holdselect

-holdbutton0

-stats <1|0>

-tiafloat <1|0>

-bs <type>

-type <type>

-channels <Mono|Stereo>

-ld <A|B>

-rd <A|B>

-tv <Color|BlackAndWhite>

-sp <Yes|No>

-lc <type>

-rc <type>

-bc <type>

-cp <Yes|No>

-format <format>

-ystart <number>

-height <number>

-pp <Yes|No>

-ppblend <number>

Command Menu

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 Section 7 - 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).

6. 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:

Item Brief description For more information, see Commandline Renderer (*) use specified rendering mode (requires restart) -video TIA Filter filter for emulation mode -tia_filter TIA Palette palette for emulation mode -palette FS Res resolution for fullscreen mode -fullres Timing (*) how to wait between frames (requires restart) -timing GL Filter OpenGL 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 Framerate frames per second in emulation mode -framerate Fullscreen mode self-explanatory -fullscreen PAL color-loss use PAL color-loss effect -colorloss GL FS Stretch stretch fullscreen OpenGL in emulation mode -gl_fsmax GL VSync enable OpenGL vertical synchronization -gl_vsync Grab mouse keep mouse in SDL window -grabmouse Center window (*) attempt to center SDL window (requires restart) -center Fast SC/AR BIOS Skip progress loading bars for SuperCharger ROMs -fastscbios

Video Settings dialog (TV Effects):

Item Brief description For more information, see Commandline TV Color Texture emulate TV pixel texturing -tv_tex TV Color Bleed emulate TV color bleed -tv_bleed TV Image Noise emulate TV RF image noise -tv_noise TV Phosphor Burn-off emulate TV phosphor mixing -tv_phos

Audio Settings dialog:

Item Brief description For more information, see Commandline Volume self-explanatory -volume Fragment size set size of audio buffers -fragsize Output freq change sound output frequency (advanced) -freq TIA freq change TIA output frequency (advanced) -tiafreq Clip volume Eliminate popping in sound generation (advanced) -clipvol Enable sound self-explanatory -sound

Input Settings dialog:

This dialog is described in further detail in Section 8 - Event Remapping.

UI Settings dialog (3 tabs):

This tab is described in further detail in Section 9 - ROM Launcher.

Item Brief description For more information, see Commandline Debugger Width/Height self-explanatory (requires restart) -debuggerres

Item Brief description For more information, see Commandline Interface Palette palette to use for UI elements -uipalette List quick delay time to wait between keypresses in listwidget -listdelay Mouse wheel scroll number of lines mouse scroll will move in listwidget -mscroll

Audit ROMs dialog:

This dialog is described in further detail in Section 10 - ROM Audit Mode.

Game Properties dialog:

This dialog allows you to change all ROM properties as described in Section 16 - Game Properties.

7. 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 Section 8 - Event Remapping). The tables below show the default settings.

Console Controls (can be remapped)

Joystick / BoosterGrip Controller (can be remapped)

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

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

Keypad Controller (can be remapped)

Developer Keys in TIA mode (cannot be remapped)

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

UI keys in Text Editing areas (cannot be remapped)

8. 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 Section 7 - 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. Erase a mapping by clicking 'Erase', or cancel a remap in progress by clicking 'Cancel'.
6. Reset default mappings by clicking 'Defaults'.

The following screenshots illustrate the event remapping process:

Virtual devices can be configured under the 'Virtual Devs' tab, shown below:

Item Brief description For more information, see Commandline Stelladaptor X is Specifies which virtual port each Stelladaptor uses (See Section 11 - Stelladaptor Support) -sa1 & -sa2 Joy deadzone Joystick deadzone area for analog joysticks -joydeadzone Mouse is paddle The mouse can emulate either paddle 0, 1, 2, or 3.   Paddle speed Speed used when emulating a paddle using a digital device -pspeed AVox serial port Described in further detail in Section 12 - AtariVox/SaveKey Support -avoxport Allow all 4 ... Allow all 4 joystick directions to be pressed simultaneously -joyallow4

9. 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 where 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. Override properties: Selecting this option shows a dialog whereby ROM properties can be temporarily overriden. Selecting options from this dialog will cause all ROMs launched after that to use those properties you specify. Clicking Default will disable its functionality, and use ROM properties as defined by the ROM itself. The dialog is as follows (See Section 16 - Game Properties for more information concerning ROM properties):

   Item For more information, see Commandline Bankswitch type -bs Left Difficulty -ld Right Difficulty -rd TV Type -tv Hold Select down -holdselect Hold Reset down -holdreset Hold Button 0 down -holdbutton0

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 Ctrl/Cmd-R key combo.

10. 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:

• THIS OPERATION CANNOT BE UNDONE. I cannot stress this enough; if you aren't completely sure you want to rename your ROMs, don't use this function. There is no undo feature, and one won't be added.
• Only filenames that Stella considers to be valid ROMs will be considered. Currently, this means files that end in '.a26', '.bin', '.rom', '.gz' and '.zip'. Files which don't have these extensions will be ignored.
• If a valid ROM doesn't have a properties entry, it will be ignored.

11. Stelladaptor Support

Stella supports real Atari 2600 joysticks, paddles and driving controllers using the Stelladaptor device.

Stella can use up to two Stelladaptors; any extra ones are ignored. Stelladaptor devices will be automatically detected and configured. Devices 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:

• The first Stelladaptor found will act as the left game port on a real Atari. Depending on the device, Stella will detect it as either the left joystick, paddles 0 & 1, or the left driving controller.
• The second Stelladaptor found will act as the right game port on a real Atari. Depending on the device, Stella will detect it as either the right joystick, paddles 2 & 3, or the right driving controller.
• Any other Stelladaptors will be ignored.
• The assignment ordering of Stelladaptor to port can be redefined with 'sa1' and 'sa2' (see description in 'Starting a Game').

12. 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 'Virtual Devs' tab in 'Input Settings', as described in Section 8.

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 OSX tend to use names similar to '/dev/xxxxxx'. For now, only Linux/UNIX, OSX, and Win32 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 '-eepromdir' commandline argument and within the application itself (see Section 5 - Starting a Game). If the path for these files hasn't been set, the default location will depend on the version of Stella, as follows:

Linux/Unix	$HOME/.stella/atarivox_eeprom.dat $HOME/.stella/savekey_eeprom.dat
Macintosh	$HOME/.stella/atarivox_eeprom.dat $HOME/.stella/savekey_eeprom.dat
Windows	%APPDATA%\Stella\atarivox_eeprom.dat %APPDATA%\Stella\savekey_eeprom.dat    OR _BASEDIR_\atarivox_eeprom.dat _BASEDIR_\savekey_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.

13. Developer Options/Integrated Debugger

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

• Developer key-combo shortcuts, used to change TIA state dynamically (ie, while the emulation is still running). See the Developer Keys in TIA mode options under Section 7 - Keyboard Layout for more information.
• Commandline options influencing emulation state. See the Command Line options under Section 5 - Starting a Game) for more information.
• Viewing TIA/console information overlaid on the TIA image. This option can be enabled from the commandline or using the Alt/ShiftCmd-L key combo, and is extremely useful for viewing the current scanline count and associated frames per second, bankswitch and display formats, etc. The following shows an example of this information:

  

  The two lines of output describe the following:

  1. Number of scanlines in current frame, associated framerate, and resulting display format. Note that the framerate shown is the internal, virtual framerate (it's calculated from the number of scanlines). If the '*' character is present, it means the display format was auto-detected as shown. For the given example, the format was auto-detected as 'NTSC'.
  2. Cartridge information. If the '*' character is present, it means the bankswitch format was auto-detected as shown. The item in round brackets indicates ROM size. For the given example, the bankswitch type was auto-detected as 4K, and the file size was 4K (4096 bytes).

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

14. 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:

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 $HOME/Library/Preferences/StellaOSX.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_)

15. 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:

• Per-frame RAM cheats:
  Evaluated each frame, and apply to RAM only. Format as follows:

     4-digit code: c041
     c0 = address
     41 = data
  	

• Cheetah codes, which are explained in detail on Bob Colbert's web page, along with a list of codes for various games. Cheetah codes don't support bankswitched ROMs, so they only work for 2K or 4K ROMs. Format as follows:

     6-digit (cheetah) code: aaaddc
     aaa = address - $f000
     dd = data
     c = count - 1
  	

• Stella extended cheats are similar to Cheetah codes, except that they can be 7 or 8 digits long, with the extra digits used for the bank number:

     7-digit (stella) code: baaaddc
     b = bank (0 to $f)
     aaa = address - $f000
     dd = data
     c = count - 1
  
     8-digit (stella) code: bbaaaddc
     bb = bank (0 to $ff)
     aaa = address - $f000
     dd = data
     c = count - 1
  	

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 Section 5 - Starting a Game). 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	$HOME/.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.

16. 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 stella.pro file. This per-user 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.

Properties

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

The name of the properties file is configurable through the '-propsfile' commandline argument and within the application itself (see Section 5 - Starting a Game). 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.pro
Macintosh	$HOME/.stella/stella.pro
Windows	%APPDATA%\Stella\stella.pro    OR _BASEDIR_\stella.pro    (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.

17. 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.

Support for a user-defined palette is a new feature for Stella 2.3, and is further described as follows:

• The palette file must be at least 792 bytes long. Colours are stored in 24-bit RGB, with the first byte for red, the second for green, the third for blue, for a total of 3 bytes per colour.
• The first 384 bytes of the file (128 * 3) will be used for the NTSC palette. The next 384 bytes (128 * 3) will be for the PAL palette. The next 24 bytes (8 * 3) will be for the SECAM palette, which consists of eight distinct colours. Any extra data in the file will be ignored.
• The PAL colour-loss effect is calculated within Stella. You do not need to specify those colours in the palette file.

The name of the palette file is configurable through the '-palettefile' commandline argument and within the application itself (see Section 5 - Starting a Game). 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	$HOME/.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.

18. Acknowledgments

Bradford W. Mott started developing Stella during the fall of 1995 and since then 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. The following is an incomplete list of the people who have played a part in bringing Stella to you. If I've missed someone, please let me know.

19. License and Disclaimer

GNU GENERAL PUBLIC LICENSE

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.

Preamble

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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.

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