Stella

## A multi-platform Atari 2600 VCS emulator

#### Release 2.3

## User's Guide

1. Introduction
2. What You Will Need
3. Installation
4. Games
5. Starting A Game
6. Changing Options
7. Settings File
8. Keyboard Layout
9. Event Remapping
10. Cheatcode Manager
11. Integrated Debugger
12. Game Properties
13. Stelladaptor Support
14. Palette Support
15. Acknowledgments
16. License and Disclaimer

February 1999 - December 2006
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

# 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, Sega Dreamcast, Unix, and Windows.

## New in Release 2.3

- Potentially huge speedups in software rendering mode, both in emulation and UI modes. Deactivating 'dirty rects' uses these new modes, which can be 2-3 times faster for many configurations.
- For UI navigation, changed from using 'joymouse' to the more familiar 'tabbing' functionality, where you move from object to object by use of some tab key. As a result, completely removed the 'joymouse' commandline argument and all associated functionality.
- Added event remapping for UI events, separate from events while in emulation mode.
- Added support for PAL60 ROMs, which use the PAL palette and resolution but run at NTSC timing (60Hz). Added ROM property for this, and updated the internal properties database for many PAL60 ROMs.
- Added support for user-definable palettes. For now, only one extra palette is supported, but in the future we may have them specified per-ROM.
- Fixed bug in PAL colour-loss emulation, which wasn't actually being done for the original Stella and z26 palettes.
- Fixed several TIA-related emulation bugs as reported on AtariAge. More fixes will come with the TIA rewrite, due in the next release.
- Added new scaler infrastructure, replacing the '-zoom' commandline argument with '-scale_ui' and '-scale_tia'. This means the UI and emulation can now be scaled independently. In the future, support will be added for advanced scalers in TIA mode, such as Scale2x, Scale3x, HQ2x, HQ3x, etc.
- Added '-gl_vsync' commandline argument and associated UI elements, which uses synchronization to vertical blank interrupt in OpenGL on supported systems. This eliminates tearing in OpenGL rendering.
- Changed naming of snapshots and state files. These files are now named based on the names given in the properties database, and no longer use the 'md5sum' name. As a result, state files from previous versions will no longer work unless they're manually renamed. Related to this, removed the '-ssname' commandline argument.
- Fixed bug where 'Snapshot saved' appeared when taking snapshots in succession.
- Added a 'Previous directory' entry to the top of each listing while in ROM Browse mode, which is equivalent to the 'Go Up' button. This makes it easier to navigate the filesystem, since you never have to 'tab out' of the ROM listing.
- Added all sound related commandline options to the UI, so you no longer have to use the commandline to set those options.
- Added new property to ROM properties specifying whether to swap paddles plugged into a virtual port. This eliminates the need to manually set the paddle mode for those ROMs that don't use paddle zero by default.
- Added a 'Defaults' button to the Game Properties dialog, which resets the ROM properties to the internal defaults, deleting that ROMs properties from the external properties file.
- Fixed bug whereby modified ROM properties weren't being reloaded when restarting a ROM.
- Made 'phosphor' and 'phosphor blend' a ROM property, meaning it can be set per-ROM.
- Added support for relocating the base Stella directory, by setting the environment variable 'STELLA_BASEDIR'. This must be done each time before Stella starts.
- Added '-fastscbios' commandline argument, which speeds up loading of vertical bars in Supercharger ROMs, and made it the default.
- Added '-autoslot' commandline argument, which automatically switches to the next available slot after saving a state. This defaults to off, and must be set from the commandline.
- Updated configure/build toolchain so patching is no longer required for Debian packages.
- Removed dependency on PNG library (PNG snapshots are still present, but the actual library is no longer required).
- For the GP2X port, added support for PAL ROMs, and updated SDL to use hardware scaling.

## 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 one Atari 2600 Paddle Controller using your computer's mouse
- Support for real Atari 2600 controllers using the Stelladaptor
- Emulates the Atari 2600 Driving Controllers using your computer's keyboard or joysticks
- Emulates the CBS Booster-Grip Controller using your computer's keyboard or joysticks
- Supports cartridges using Atari's standard 2K and 4K format
- Supports cartridges using Atari's 8K, 16K, and 32K bank-switching schemes
- Supports cartridges using Activision's 8K bank-switching scheme (Robot Tank and Decathlon)
- Supports cartridges using CBS Electronics' 12K bank-switching scheme
- Supports cartridges using Chris Wilkson's Megacart 128K bank-switching scheme
- Supports cartridges using Commavid bank-switching scheme
- Supports cartridges using M-Network's 16K bank-switching scheme
- Supports cartridges using Parker Brothers' 8K bank-switching scheme
- Supports cartridges using Tigervision's bank-switching scheme with up to 512K ROM
- Supports cartridges using UA Limited bank-switching scheme
- Supports Supercharger single-load and multi-load games
- Supports property file for setting the properties associated with games
- Supports user specified frame rate
- Supports the NTSC, PAL and PAL60 television standards
- Supports several "undocumented features" of the TIA graphics chip used by some games
- TIA emulation supports full collision checking

# 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 1.2.0 or greater, version 1.2.11 highly recommended
- Latest version of the zlib library
- Joysticks or gamepads are highly recommended
- Mouse or Stelladaptor with real paddles required for paddle emulation
- Some ROM images (no, we won't tell you where to find them)

## 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
- GNU C++ compiler version 2.95 and the make utility are required for compiling the Stella source code; GNU C++ compiler version 3.2.x/4.x or later is highly recommended
- Pentium class machine required (Stella may compile on other architectures, but it hasn't been extensively tested)

## Macintosh

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

- Mac OSX 10.2 or Above
- 500 MHz G4 PPC/Intel processor or above (Stella may work with a G3 processor, but this is still a work-in-progress)
- OpenGL capable video card. Software rendering mode is still available, but as of OSX 10.4 is substandard compared to OpenGL.

## Windows

The Windows version of Stella is designed to work on Windows 98/ME/2000/XP with the following:

- Visual C++ 7 or MinGW compiler is required to compile the Stella source code
- Pentium class machine required; OpenGL accelerated video card highly recommended
- SDL version 1.2.8 or greater (or included SDL.dll) required for Stelladaptor support

# 3. Installation

Stella is distributed in both source and binary form. 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

- Compressed tarball (stella-release-src.tar.gz)

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

- Source RPM (stella-release-1.src.rpm)

1. Rebuild the archive with the following command:

          rpmbuild --rebuild stella-release-1.src.rpm

2. Follow the instructions under Binary RPM to install the stella-release-1.ix86.rpm file

- Binary RPM (stella-release-1.ix86.rpm)

1. Install the binary RPM with the following command:

          rpm -Uvh stella-release-1.ix86.rpm

## Macintosh

To install the Mac binary, simply download the DMG disk image. Mount the disk image, then copy the StellaOSXrelease folder to your hard drive.

## Windows

- Compressed tarball (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. If compiling the Stella executable using MinGW, use the same commands as specified under Linux/UNIX - Compressed tarball
3. If compiling using Visual C++ 7:

- Open the stella-release/src/win32/Stella.sln file using Visual C++ 7
- Build the 'Stella' solution
- Copy the Stella.exe and stella.pro files to some directory

- Binary ZIP file (stella-release-win32.zip)

1. Unzip the binary ZIP file using Winzip or Total Commander and copy that directory somewhere

- Binary EXE installer (stella-release-win32.exe)

1. Double-click on the installer and follow the onscreen instructions

# 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

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.

# 5. Starting A Game

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

## Integrated GUI

As of Stella version 2.0, there is an integrated GUI for all ports. This means that using the commandline is no longer required (but commandline support is still included 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:

The ROM and snapshot settings may be changed by clicking the 'Options' button:

Selecting a new path for ROM or snapshots is done by clicking the 'Path' button(s):

Once a ROM directory has been selected, clicking 'Reload' will update the ROM listing. You can start emulation by selecting a ROM and pressing 'Enter' or clicking 'Play', or double-clicking a ROM.

## Command Line

Stella can also be used from the commandline (assuming your operating system has a commandline). When using this mode, the ROM launcher is disabled.

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

       stella [options ...] filename.bin

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

Argument | Description
--- | ---
    -video <soft|gl>
| Use SDL 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 OSX, this should probably be left blank.
    -gl_filter <nearest|linear>
| OpenGL mode only. Use GL_NEAREST or GL_LINEAR filtering. GL_NEAREST results in a scaled, pixelated image, while GL_LINEAR introduces blurring.
    -gl_aspect <number>
| OpenGL mode only. Specify the aspect ratio of the window. Normal TV mode would be 4:3, so you would specify 1.3333. But since many video modes do not use square pixels, you may have to try different values. I find 1.6 or 1.7 gives the most authentic look.
    -gl_fsmax <0|1>
| OpenGL mode only. Use the current desktop resolution when switching to fullscreen OpenGL mode (so a video-mode switch can be avoided). If not supported, then use the maximum possible resolution available.
    -gl_vsync <0|1>
| OpenGL mode only. Synchronize screen updates to the vertical blank period. This can result in smoother updates, and eliminate tearing.
    -scale_tia <scaler>
| Use the specified scaler while in TIA/emulation mode. Possible scalers are 'zoom1x, ..., zoom6x'.
    -scale_ui <scaler>
| Use the specified scaler while in UI mode (currently, the ROM launcher and debugger). Possible scalers are 'zoom1x, ..., zoom6x'.
    -fullscreen <0|1>
| Play the game in fullscreen mode.
    -center <0|1>
| Centers game window (if possible).
    -grabmouse <0|1>
| Keeps the mouse in the game window.
    -palette <original|standard|z26|user>
| Set the palette to either pre-Stella 1.4, Stella 1.4 and above, the palette used in the z26 emulator, or a user-defined palette.
    -framerate <number>
| Display the given number of frames per second. Normally, Stella will determine framerate based on ROM format.
    -sound <1|0>
| Enable or disable sound generation.
    -channels <1|2>
| Enable mono or stereo sound.
    -fragsize <number>
| Specify the sound fragment size to use. Linux/Mac seems to work with 512, Windows may need 2048.
    -freq <number>
| Set sound sample output frequency (0 - 48000). Default is 31400.
    -tiafreq <number>
| Set sound sample generation frequency (0 - 48000). Default is 31400.
    -volume <number>
| Set the volume (0 - 100).
    -clipvol <1|0>
| Enable volume clipping (eliminates popping).
    -cheat <code>
| Use the specified cheatcode (see Cheat section for description).
    -showinfo <0|1>
| Shows some game info while Stella is running.
    -paddle <0|1|2|3>
| Indicates which paddle the mouse should emulate (defaults to paddle 0).
    -sa1 <left|right>
| Stelladaptor 1 emulates specified joystick port.
    -sa2 <left|right>
| Stelladaptor 2 emulates specified joystick port.
    -p0speed <number>
| Speed of digital emulation for paddle 0 (0-100).
    -p1speed <number>
| Speed of digital emulation for paddle 1 (0-100).
    -p2speed <number>
| Speed of digital emulation for paddle 2 (0-100).
    -p3speed <number>
| Speed of digital emulation for paddle 3 (0-100).
    -pthresh <number>
| Set threshold for eliminating paddle jitter.
    -tiadefaults <1|0>
| Use TIA positioning defaults instead of enhanced values. The default values result in the image appearing as it does on a real 2600 system (in most cases).
    -rombrowse <1|0>
| The ROM listing is treated as a filesystem, where one can traverse folders. As of Stella 2.3, this is the default browsing mode.
    -autoslot <1|0>
| Automatically switch to the next available save state slot after saving a ROM state file.
    -fastscbios <1|0>
| Set loading of Supercharger BIOS bars to maximum speed (8x normal).
    -accurate <1|0>
| Linux only, may be removed in future versions. Use this when running under the Linux 2.4 kernel. Otherwise, this should probably not be used.
    -ssdir <path>
| The directory to save snapshot files to.
    -sssingle <0|1>
| Generate single snapshot instead of many.
    -listrominfo
| Prints relevant contents of the Stella ROM database, one ROM per line, and then exit Stella. This can be used for external frontends.
    -help
| 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
--- | ---
    -break <address>
| Set a breakpoint at specified address.
    -debugheight <number>
| Set height of debugger in lines of text (currently not 100% working)
    -debug
| Immediately jump to debugger mode when starting Stella.
    -holdreset
| Start the emulator with the Game Reset switch held down.
    -holdselect
| Start the emulator with the Game Select switch held down.
    -holdbutton0
| Start the emulator with the left joystick button held down.
    -pro <props file>
| Use the given properties file instead of stella.pro.
    -type <type>
| Set "Cartridge.Type" property. See the Game Properties section for valid types.
    -ld <A|B>
| Set "Console.LeftDifficulty" property.
    -rd <A|B>
| Set "Console.RightDifficulty" property.
    -tv <Color|BlackAndWhite>
| Set "Console.TelevisionType" property.
    -lc <type>
| Set "Controller.Left" property, where type is one of Booster-Grip, Driving, Keyboard, Paddles, or Joystick.
    -rc <type>
| Set "Controller.Right" property, where type is one of Booster-Grip, Driving, Keyboard, Paddles, or Joystick.
    -bc <type>
| Sets both "Controller.Left" and "Controller.Right" properties, where type is one of Booster-Grip, Driving, Keyboard, Paddles, or Joystick.
    -cp <Yes|No>
| Set "Controller.SwapPaddles" property.
    -format <NTSC|PAL>
| Set "Display.Format" property.
    -xstart <number>
| Set "Display.XStart" property (0 - 80).
    -ystart <number>
| Set "Display.YStart" property (0 - 64).
    -width <number>
| Set "Display.Width" property (80 - 160).
    -height <number>
| Set "Display.Height" property (100 - 256).
    -pp <Yes|No>
| Set "Display.Phosphor" property.
    -ppblend <number>
| Set "Display.PPBlend" property, used for phosphor effect (0-100). Default is 77.
    -hmove <Yes|No>
| Set "Emulation.HmoveBlanks" property.

# 6. Changing Options

As of version 2.0, all settings can be changed within the integrated Options GUI while Stella is running. The options are documented elsewhere in this manual and are generally self-explanatory.

Video Options dialog:

Audio Options dialog:

Game Information dialog:

Help dialog:

About dialog:

# 7. 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
-showinfo 1 | showinfo = 1 (or showinfo = true)

The settings file has a special name/location depending on which version of Stella you use. Note that if the environment variable 'STELLA_BASEDIR' is set, the location of the settings file will change accordingly:

## Linux/UNIX

The Linux and UNIX version of Stella searches for the stellarc file in your $HOME/.stella directory, or in $STELLA_BASEDIR if that environment variable is set.

## Macintosh

The Macintosh version does not use an INI file, but stores it preferences in the expected location for application preferences, in the Users home directory, in the Library/Preferences/StellaOSX.plist file. The STELLA_BASEDIR environment variable has no effect for the settings file in OSX.

## Windows

The Windows version of Stella looks for the stella.ini file in the same directory containing the application, or in $STELLA_BASEDIR if that environment variable is set. Future versions of Stella for Windows may look in user-specific locations (C:\Documents and Settings\...).

# 8. Keyboard Layout

The Atari 2600 console controls and controllers are mapped to the computer's keyboard as shown in the following tables.

As of Stella 1.4, most of these events can be remapped to other keys on your keyboard or buttons on your joystick (see Section 9 - Event Remapping). The tables below show the default settings.

Console Controls

Function | Key (Standard) | Key (OSX)
--- | --- | ---
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 B | F5 | F5
Left Player Difficulty A | F6 | F6
Right Player Difficulty B | F7 | F7
Right Player Difficulty A | 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 | Pause

Joystick Controller

Left Joystick | Right Joystick
--- | ---
Function | Key
--- | ---
Joystick Up | Up arrow
Joystick Down | Down arrow
Joystick Left | Left arrow
Joystick Right | Right arrow
Fire Button | Space
Function | Key
--- | ---
Joystick Up | Y
Joystick Down | H
Joystick Left | G
Joystick Right | J
Fire Button | F

Booster-Grip Controller

Left Booster-Grip | Right Booster-Grip
--- | ---
Function | Key
--- | ---
Booster-Grip Up | Same as left joystick
Booster-Grip Down | Same as left joystick
Booster-Grip Left | Same as left joystick
Booster-Grip Right | Same as left joystick
Fire Button | Same as left joystick
Trigger Button | 4
Booster Button | 5
Function | Key
--- | ---
Booster-Grip Up | Same as right joystick
Booster-Grip Down | Same as right joystick
Booster-Grip Left | Same as right joystick
Booster-Grip Right | Same as right joystick
Fire Button | Same as right joystick
Trigger Button | 6
Booster Button | 7

Driving Controller

Left Driving | Right Driving
--- | ---
Function | Key
--- | ---
Left Direction | Insert
Right Direction | Page Up
Fire Button | Home
Function | Key
--- | ---
Left Direction | Delete
Right Direction | Page Down
Fire Button | End

Keypad Controller

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 | .
# | /

Developer Keys (can't be remapped)

Function | Key (Standard) | Key (OSX)
--- | --- | ---
Set "Display.YStart" to next larger value | Alt + PageUp | Shift-Cmd + PageUp
Set "Display.YStart" to next smaller value | Alt + PageDown | Shift-Cmd + PageDown
Set "Display.Height" to next larger value | Control + PageUp | Cmd + PageUp
Set "Display.Height" to next smaller value | Control + PageDown | Cmd + PageDown
Set "Display.XStart" to next larger value | Alt + End | Shift-Cmd + End
Set "Display.XStart" to next smaller value | Alt + Home | Shift-Cmd + Home
Set "Display.Width" to next larger value | Control + End | Cmd + End
Set "Display.Width" to next smaller value | Control + Home | Cmd + Home

Other Keys (can't be remapped)

Function | Key (Standard) | Key (OSX)
--- | --- | ---
Switch to next larger scaler | Alt + = | Cmd + =
Switch to next smaller scaler | Alt + - | Cmd + -
Toggle fullscreen/windowed mode | Alt + Enter | Cmd + Enter
Increase volume | Alt + ] | Shift-Cmd + ]
Decrease volume | Alt + [ | Shift-Cmd + [
Grab mouse (keep mouse in game window) | Control + g | Cmd + g
Toggle display format between NTSC, PAL, PAL60 | Control + f | Cmd + f
Save current properties to a new properties file | Control + s | Cmd + s
Set mouse to emulate paddle 0 | Control + 0 | Cmd + 0
Set mouse to emulate paddle 1 | Control + 1 | Cmd + 1
Set mouse to emulate paddle 2 | Control + 2 | Cmd + 2
Set mouse to emulate paddle 3 | Control + 3 | Cmd + 3
Reload current ROM | Control + r | Cmd + r
Emulate 'frying' effect | Backspace | Backspace
Toggle 'phosphor' effect | Alt + p | Shift-Cmd + p
Toggle palette | Control + p | Cmd + p

# 9. Event Remapping

This version of Stella has event remapping. Almost every event in the emulator can be remapped to another key on the keyboard or to buttons on up to four joysticks/gamepads (see Section 8 - Keyboard Layout for those event which can/cannot be remapped).

To remap an event:

1. Start playing a game (ie, start the emulation).
2. Enter options mode be pressing Tab.
3. Click the 'Input Settings' button.
4. Click the 'Event Mapping' tab.
5. Select event you want to remap and click the 'Map' button.
6. 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.
7. Erase a mapping by clicking 'Erase', or cancel a remap in progress by clicking 'Cancel'.
8. Reset default mappings by clicking 'Defaults'.
9. Change mouse/paddle emulation in the 'Mouse is paddle' dropdown box.

The following screenshots illustrate the event remapping process:

# 10. Cheatcode Manager

Stella 2.0 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

# 11. Integrated Debugger

Have a look at this page for integrated debugger documentation.

# 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 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.

## Linux/Unix

The Linux and Unix versions of Stella looks for your personal properties file in $HOME/.stella/stella.pro, or if the STELLA_BASEDIR environment variable is set, in $STELLA_BASEDIR/stella.pro.

## Macintosh

The Mac version of Stella looks for your personal properties file in $HOME/.stella/stella.pro, or if the STELLA_BASEDIR environment variable is set, in $STELLA_BASEDIR/stella.pro.

## Windows

The Windows version of Stella looks for the properties file in the directory containing the application, or if the STELLA_BASEDIR environment variable is set, in $STELLA_BASEDIR/stella.pro. Future versions of Stella for Windows may look in user-specific locations (C:\Documents and Settings\...).

## 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.Name"      "Value"
       "Property"            "Value"
       ""

       ; Comments
       "Cartridge.Name"      "Value"
       "Property"            "Value"
       ""

       . . .

       ; Comments
       "Cartridge.Name"      "Value"
       "Property"            "Value"
       ""

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

## Properties

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

Cartridge.MD5: | This property 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: | This property indicates the game's manufacturer. Currently this property is not being used, however, future versions of Stella will probably allow the user to view this information.
Cartridge.ModelNo: | This property indicates the manufacturer's model number for the game. Currently this property is not being used, however, future versions of Stella will probably allow the user to view this information.
Cartridge.Name: | This property indicates the actual name of the game.
Cartridge.Note: | This property contains any special notes about playing the game.
Cartridge.Rarity: | This property indicates how rare a cartridge is, based on the scale described on AtariAge.
Cartridge.Sound: | This property determines 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 of this property must be Mono or Stereo.
Cartridge.Type: | This property indicates the bank-switching type for the game. The value of this property must be: Auto-detect, 2K, 3E, 3F, 4K, AR, CV, DPC, E0, E7, F4, F4SC, F6, F6SC, F8, F8SC, FASC, FE, MB, MC or UA. For more information about bank-switching see Kevin Horton's 2600 bank-switching document.
Console.LeftDifficulty: | This property indicates the default difficulty setting for the left player. The value of this property must be A or B.
Console.RightDifficulty: | This property indicates the default difficulty setting for the right player. The value of this property must be A or B.
Console.TelevisionType: | This property indicates the default television setting for the game. The value of this property must be Color or BlankAndWhite.
Console.SwapPorts: | This property indicates that the left and right ports should be swapped internally. This is used for ROMs like 'Raiders' where the Player 1 joystick is plugged into the right joystick port. The value of this property must be Yes or No.
Controller.Left: | This property indicates what type of controller the left player uses. The value of this property must be Booster-Grip, Driving, Keyboard, Paddles, or Joystick.
Controller.Right: | This property indicates what type of controller the right player uses. The value of this property must be Booster-Grip, Driving, Keyboard, Paddles, or Joystick.
Controller.SwapPaddles: | This property 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 of this property must be Yes or No.
Display.Format: | This property indicates the television format the game was designed for. The value of this property must be NTSC, PAL or PAL60.
Display.XStart: | This property indicates the horizontal location to start displaying pixels at on a scan-line. The value of this property must be n such that 0 <= n <= 80 and n is divisible by 4.
Display.Width: | This property indicates the number of pixels to display per scan-line. The value of this property must be n such that 80 <= n <= 160 and n is divisible by 4.
Display.YStart: | This property indicates the scan-line to start displaying at. The value of this property must be n such that 0 <= n <= 64.
Display.Height: | This property indicates the number of scan-lines to display. The value of this property must be n such that 100 <= n <= 256.
Display.Phosphor: | This property indicates whether the phosphor effect should be emulated or not. The value of this property must be Yes or No.
Display.PPBlend: | This property indicates the amount of blending which will occur while using the phosphor effect. The value of this property must be n such that 0 <= n <= 100. The default value is 77.
Emulation.HmoveBlanks: | This property indicates whether the TIA HMOVE blank bug should be emulated or not. The value of this property must be Yes or No.

# 13. 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 emulation is running; Stella will detect the change and act accordingly.

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 1 & 2, 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 3 & 4, 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').

# 14. Palette Support

An Atari 2600 palette consists of 128 colours, which are different for the two major television standards (NTSC and PAL/PAL60). Stella supports three 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.
original | The palette used in the original StellaX.
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 called 'stella.pal', and will be located in the base folder, in the same place as the stella properties file.
- The palette file must be at least 768 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 second 384 bytes will be for the PAL/PAL60 palette. 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.

In the future, support may be added for specifying a palette for each ROM.

# 15. 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:

Stephen Anthony | Ported Stella 1.1 to SDL. Added extra command line options to X11/SDL versions. Added INI file support, faster startup, snapshot support, and pause functionality to core. Converted Stella 1.1 manual to HTML. Ported codebase to SDL for Windows/MacOSX. Added OpenGL support and Stelladaptor support. Current maintainer for the Linux and Windows versions.
David Aspell | Ported release 0.7 of Stella to Java
Christopher Bennett | Helped discover a Superchanger emulation bug in release 1.0 of Stella
Alexander Bilstein | Provided "A Brief History of the Atari 2600" for this manual
Dan Boris | Provided technical information on the Supercharger
Piero Cavina | Allowed "Oystron" to be included in the Stella distribution
Bob Colbert | Allowed "Okie Dokie" to be included in the Stella distribution
Joe D'Andrea | Author of the IRIX port of Stella until release 1.2
Renato Ferreira | Provided code to support private colormaps under Unix
Ron Fries | Author of the awesome TIA Sound library
Aaron Giles | Author of the Power Macintosh version of Stella until release 1.1
Mark Grebe | Author of the Macintosh OSX version of Stella starting with the 1.4 release. Helped with Stelladaptor support.
Mark Hahn | Allowed "Elk Attack" to be included in the Stella distribution and provided help with the TIA HMOVE blank bug
Kevin Horton | Author of the definitive Atari 2600 bank-switching document
Thomas Jentzsch | Provided updated NTSC palette and many ideas
Kostas Nakos | Author/maintainer of the WinCE version of Stella starting with the 2.0 release
Erik Kovach | Author of the property file for release 0.7, 1.0, 1.1, and 1.2 of Stella
Daniel Marks | Provided improved keyboard joystick support for Stella release 0.1
James Mcclain | Provided patches for the 1.2 release to get Stella to compile with GCC 3.0
David McEwen | Author of the Acorn version of Stella
Jeff Miller | Author of the Windows version of Stella until release 1.2
Dan Mowczan | Provided a Supercharger to help with Stella's development
Jack Nutting | Author of the OpenStep version of Stella
Manuel Polik | Author of the Windows version of Stella starting with the 1.2 release
Jim Pragit | Author of the "Game Menu" emulator game shell
John Saeger | Participated in a helpful discussion on understanding the TIA's RESPx multi-sprite trick
Chris Salomon | Provided information and code to help implement Supercharger support
Jason Scott | Organizer of the property file archive for early versions of Stella; now he's helping with the web site
David Shaw | Provided make targets for the BSDI platform
Raul Silva | Helped with design and graphics for an early version of the Stella web site
Chris Snell | Maintained a mirror of the Stella FTP site
Darrell Spice Jr. | Author of the OS/2 version of Stella
John Stiles | Maintained the Macintosh version of Stella until release 1.2
Eckhard Stolberg | Provided a description of the TIA bug that produces the star field effect in Cosmic Ark, provided the PAL television palette, and participated in a helpful discussion on understanding the TIA's RESPx multi-sprite trick. He also provided the Commavid and Megaboy support for Stella as well as some improved Supercharger BIOS code.
Matthew Stroup | Author of the Amiga version of Stella
Joel Sutton | Author of the FreeBSD version of Stella
Greg Troutman | Allowed "This Planet Sucks" to be included in the Stella distribution
Curt Vendel | Provided schematics of the TIA which are being used to improve the TIA emulation.
David Voswinkel | Maintainer of the PSP version of Stella starting with the 2.0 release
Brian Watson | Helped with getting the illegal CPU instruction support working with Stella. Brian also submitted a number of other changes, such as debugger support, which have been finally integrated into the 2.0 release of Stella. Without a doubt, there would be no debugger support in Stella if not for the tireless work of Brian.
Keith Wilkins | Maintained the DOS version of Stella until release 0.7
Jeff Wisnia | Provided technical data sheet for the 6532 RIOT chip
Alex Zaballa | Maintainer of the GP2X version of Stella starting with the 2.1 release

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

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

NO WARRANTY

11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.