EMU7800: A .NET Atari 7800 Emulator

v0.81, February 28, 2007
Mike Murphy, mimurphy@users.sourceforge.net

EMU7800 releases can be downloaded from SourceForge here.

Click here to jump to the Keyboard Mappings.

Click here to jump to the Screenshot Gallery.

1.0 Introduction
    1.1 Copyright Notice, Disclaimer, License
    1.2 Release Notes
    1.3 Acknowledgements
    1.4 Known Issues
2.0 Installation
    2.1 Prerequisites
    2.2 Installing the Distribution
    2.3 Rebuilding from Source
    2.4 Game Cartridge Information Database (a.k.a. ROMProperties)
3.0 Running the Emulator
    3.1 Keyboard Mappings
    3.2 Game Controller/Joysticks
    3.3 Paddle and Lightgun Emulation via Mouse (SDL Host only)
    3.4 User Interface
        3.4.1 Game Select Tab
        3.4.2 Settings Tab
        3.4.3 Console Tab
        3.4.4 Help Tab
    3.5 Addressing Performance Problems
    3.6 External Command-line Options
4.0 Screenshot Gallery

1.0 Introduction

This is a release of EMU7800, an Atari 7800 emulator implemented using Microsoft's .NET platform. Most VCS (2600) and ProSystem (7800) titles work well, with 2600 support featuring authentic HMOVE emulation, per Andrew Tower's paper "A Small Opus on the TIA." The stars in Cosmic Ark appear, but without emulation cheats.

EMU7800 runs on Windows 2000, XP, 2003 and Vista. Performance is excellent on systems a year or less old.

EMU7800 was originally an academic graduate capstone project for the Institute of Technology at UW Tacoma.

Send me a note if you have questions or feedback. Enjoy!

1.1 Copyright Notice, Disclaimer, License

THIS SOFTWARE IS PROVIDED "AS-IS" WITHOUT ANY EXPRESSED OR IMPLIED WARRANTY. IN NO EVENT WILL THE AUTHOR BE HELD LIABLE FOR ANY DAMAGES ARISING FROM THE USE OF THIS SOFTWARE. PLEASE SEE THE ENCLOSED "LICENSE.TXT" FILE FOR THE COMPLETE LICENSING TERMS.

1.2 Release Notes

0.81:

Added: WPF Host (Windows Presentation Foundation) for better compatibility with Windows Vista
Updated: SDL.dll to version 1.2.11

0.71:

Added: Web browser control on new Help tab, enabling easy reference to this README and online game manuals where defined in ROMProperties.csv
Fixed: 7800 Emulation: 320B mode corrected to correspond to the real hardware—courtesy of Matthias Luedtke (matthias@atari8bit.de)
Updated: Moved to .NET 2.0 and Visual Studio 2005
Updated: SDL.dll to version 1.2.10
Added: Emulator sleeps after each frame is rendered to reduce superfluous CPU consumption (can be tuned via the Console tab)
Updated: Better pause behavior—modal functions are still available during pause

0.61:

Fixed: Emulator continued to run in the background when the window was closed
Progress meter added so the user has something to watch while large ROM directories are examined
Added: High Score Cartridge support (7800)—courtesy of Matthias Luedtke (matthias@atari8bit.de)
Added: Settings are stored in the Win32 registry, so they persist across new versions and recompiles
Updated: SDL.dll to version 1.2.8
Updated: Unified distribution into one single .MSI archive, that can build itself

0.60:

Added: Support for the Stelladaptor controller
Added: Recognizes the now correct 7800 NTSC BIOS. Old 7800 BIOS is still recognized for now, but a warning message appears on the Green Screen log. Thanks to Mitchell Orman (Mitch@atari7800.org) for the information
Numerous minor fixes and documentation updates

0.55:

Added: NOP instruction register dumping (homebrew developer support), activate on the console using cpunop on. Setting will persist between invocations
Added: Button on the Settings Tab that brings up an openfile dialog to load previously saved machine states
Added: Double-clicking on the game select tab will immediately start the selected ROM
Updated: Converted ROM database to a .CSV file: Editable via MS Excel or text editor
Fixed: PAL 7800BIOS startup
Added: Command-line ROM invocation to support various emulator front-ends
Reverted: TIASound to v0.41 version: fixes a sound omission bug
No changes to emulation were made for this release

0.50:

"The Truth in Advertising" release... now, most 7800 titles are playable
Added: 7800 BIOS startup can be skipped
Added: Both .a78 and .bin 7800 ROMs are supported
Added: Game state save/restore
Added: Mouse-based lightgun support, which works correctly for 2600 games
Added: GUI options for varying emulation speed, etc.

0.41:

Substituted use of Managed DirectX with the Simple DirectMedia Layer (SDL). Fullscreen performance is now on par with the most excellent Z26 emulator.
Solved the sound syncronization problem; audio now works perfectly.
Added: Game controller (joystick) support.
Added: mouse-based paddle emulation on SDL fullscreen mode.
No changes to emulation were made for this release.

0.33:

Further refined the HMOVE emulation, added a few illegal opcodes to enable some of the homebrew titles to work, and fixed several emulation bugs. This cleaned up Pitfall2, and other Activision titles that had visual artifacts.

Fixed: eliminated PIA bugs: no more jittering for Star Fox, Off Your Rocker, Spitfire, Omega Race, Blueprint, and others probably
Fixed: minor missle/ball positioning TIA bug
Fixed: booster grip controller now works right
Fixed: Omega Race rom was being ignored because of its odd size
Fixed: emulator no longer requires one line of VSYNC; this helps one of the Bowling ROMs and others probably

0.32:

Fixed: the file picker on the GameSelectTab hung in certain circumstances
Fixed: Pitfall2 rom was being ignored because of its odd size Cleaned up the distribution by removing some unneeded junk

0.31:

First major release via SourceForge.

1.3 Acknowledgements

EMU7800 is a derived work of many people. Please let me know should others need to be included in the following list:

Bradford W. Mott, et al., Author of the Stella emulator
John Saeger, et al., Author of the Z26 emulator
Dan Boris, Author of 7800 emulation in MESS
Andrew Towers, Author of "TIA Hardware Notes: A Small Opus on the TIA"
Ron Fries, Author of the TIASound library

For all things Atari, including game manuals, tips, and community, be sure to visit AtariAge!

1.4 Known Issues

Tetris (one scanline fast jitter)
Challenge: 4311a4115fb7bc68477c96cf44cebacf (doesnt work, needs some illegal opcodes)
Pitfall II sound needs fixin'
River Raid: Leftmost house moves a pixel to the right onscreen
Asteroids: Copyright logo on start up needs aligning
One on One Basketball (7800): Timing maybe fixed, but there are display artifacts
Xenophobe (7800): flickering/hangs
Lightgun for the 7800 is inaccurate; a timing problem
No Supercharger support
Grand Prix: "off by two CLK"
Need Pokey emulation for a couple 7800 titles (Ballblazer and Commando)
Need Mindlink controller support
Need to support more illegal CPU opcodes to better support homebrews

2.0 Installation

2.1 Prerequisites

To run EMU7800, you will need to have the .NET 2.0 runtime installed onto your Windows-based computer. You can do this via Windows Update. To use the WPF Host on Windows Vista, you will need to have the DirectX runtime installed (including the Managed DirectX libraries.) To have the capability to build from the included source code, you'll either need the .NET 2.0 software development kit (SDK) or Visual Studio 2005. EMU7800 was developed on a machine with a Pentium 4 Celeron 1.7 GHZ processor (a five year-old system, as of this writing.) This was adequate for emulator performance.

2.2 Installing the Distribution

The distribution is made available as an Windows Installer .MSI file. Simply launch it to deploy the software to your machine. A single shortcut will be placed on your desktop to launch the emulator.

2.3 Rebuilding from Source

For the curious, the complete source code is included in the distribution and is located in the src/ folder. To rebuild from source, either use Visual Studio 2005 to open the *.sln or use the following MSBuild command in a CMD.EXE window:

MSBuild /t:Rebuild /p:Configuration=Release EMU7800.csproj

The MSBuild utility is located in the %WINDIR%\Microsoft.NET\Framework\v2.0.50727 folder.

2.4 Game Cartridge Information Database (a.k.a. ROMProperties)

In EMU7800, recognized game ROM files have associated properties that determine the proper execution configuration of the emulator. These attributes are stored in the ROMProperties.CSV file, located in the same directory as the executable. Any editor that can work with .CSV files (e.g. NOTEPAD.EXE and Excel™), can be used to update the file. Note that a copy of this file is also in the src\ folder—serving as a ready backup when necessary.

3.0 Running the Emulator

3.1 Keyboard Mappings

Key	GDI Host	SDL Host	WPF Host	Function
ESC	•	•	•	Escape (quit) from the currently running machine/game
Q		•	•	Swap Stelladaptor paddles P1/P2 on device 0
W		•	•	Swap game controller/joystick devices 0/1
E		•	•	Swap Stelladaptor paddles P3/P4 on device 1
P	•	•	•	Pause the emulator, any other key resumes
M	•	•	•	Sound mute toggle
F	•	•	•	Show frame rate, emulator execution statistics
R	•	•	•	Game Reset Console Switch
S	•	•	•	Game Select Console Switch
C	•	•	•	Toggle between Color and B/W Console Switch settings
1	•	•	•	Toggle between A/B difficulty for left player
2	•	•	•	Toggle between A/B difficulty for right player
F1	•	•	•	Set keyboard/mouse to player 1 control
F2	•	•	•	Set keyboard/mouse to player 2 control
F3	•	•	•	Set keyboard/mouse to player 3 control
F4	•	•	•	Set keyboard/mouse to player 4 control
F5	•	•	•	Pan display left
F6	•	•	•	Pan display right
F7	•	•	•	Pan display up
F8	•	•	•	Pan display down
F11		•	•	Save machine state to `outdir/`
F12		•	•	Save Screenshot to `outdir/`
Up Arrow	•	•	•	Move up: joystick, booster grip
Left Arrow	•	•	•	Move left: joystick, booster grip, paddles, driving
Right Arrow	•	•	•	Move right: joystick, booster grip, paddles, driving
Down Arrow	•	•	•	Move down: joystick, booster grip
CTRL	•	•	•	Trigger
ALT	•	•	•	Booster
NUMPAD7	•	•	•	Keypad 7
NUMPAD8	•	•	•	Keypad 8
NUMPAD9	•	•	•	Keypad 9
NUMPAD4	•	•	•	Keypad 4
NUMPAD5	•	•	•	Keypad 5
NUMPAD6	•	•	•	Keypad 6
NUMPAD1	•	•	•	Keypad 1
NUMPAD2	•	•	•	Keypad 2
NUMPAD3	•	•	•	Keypad 3
NUMPAD*	•	•	•	Keypad *
NUMPAD0	•	•	•	Keypad 0
NUMPAD/	•	•	•	Keypad #

3.2 Game Controller/Joysticks

Up to two game controllers (e.g. joysticks) can be used, where the first two found in the device list will be selected for use.

For game ROMs that use the paddle controller, the mouse will be used as input unless the Stelladaptor controller is detected as one of the selected game controllers. In this case, mouse input will be automatically deactivated and the Stelladaptor device will be leveraged for paddle input.

The paddle swapping keys (Q and E) of the SDL and WPF Host are useful when you are using a set of original Atari paddles, where the "player 1" potentiometer is excessively worn and delivers non-uniform and/or erratic resistances. Chances are the "player 2" dial has not seen as much action and will perform better.

3.3 Paddle and Lightgun Emulation via Mouse (SDL and WPF Host)

On paddle games, the mouse can be used as the paddle controller. Sensitivity is currently not configurable. The mouse is also be used for lightgun games. Look for a small white dot that indicates where on the screen the "lightgun" is pointed at.

3.4 User Interface

3.4.1 Game Select Tab

Game Select Tab

The number of ROMs recognized in the roms/ directory is displayed in the lower left corner. To select a new directory, click the Select ROM File button, and navigate to the ROM directory of your choice. When a ROM file is selected, the rest of the directory contents will be scanned and will be presented for subsequent selection.

Open File Dialog

By default, .bin files will be displayed in the Open File dialog. To show .a78 files, use the File Type drop-down.

3.4.2 Settings Tab

Settings Tab

There are several settings that can be adjusted on this tab. Settings will saved, so they will not need to be set again every time the program is launched.

Host Select: There are three "hosts" available to run the emulated machinery. They are: Windows GDI (GDI Host), Simple DirectMedia Layer (SDL Host), and Windows Presentation Foundation (WPF Host). The GDI Host is not the best for game playing, but is good for emulator development and testing. It does not operate in full-screen mode, and not all controller features are supported. Further, video performance degrades proportional to the amount of differences between frames. For the best game-playing experience, choose the SDL Host for pre-Vista systems and WPF Host for Vista systems.
Frame Rate Adjust: Default framerate for NTSC (N. American T.V. standard) games is 60hz, while the default framerate for PAL (European T.V. standard) games is 50hz. Should you find that your computer is not fast enough to run the emulator, you can adjust the framerate down as appropriate. Persistant audio popping indicates the sound queue is underflowing—indicating the emulator is unable to run fast enough to keep it filled. Note that reducing the framerate also scales down the audio playback frequency accordingly, so the audio pitch will decrease. Audio playback is used to throttle the display framerate—so both are tightly coupled.
Sound Queue Length: Reducing the queue length reduces the sound latency, but increases the risk of the sound queue underflowing that causes spurious audio popping. Correspondingly, increasing the queue length increases the sound latency, but decreases the risk of the sound queue underflowing. Also, it seems Windows likes to read ahead by 8 buffers on Vista. Of course your mileage may vary, but the default setting of 10 buffers should be sufficient in most cases.
Sound Volume: Adjusts the sound volume. In many cases, this will not need to be adjusted as the volume knob on your PC speakers may work just as well.
Skip BIOS (7800 Emulation): The real Atari 7800 executes BIOS code on machine startup. To do this on the emulator, the BIOS ROM(s) (one for NTSC, and one for PAL) need to be in the current ROM directory and this checkbox needs to be unchecked. If you do not have the BIOS files or just want to skip BIOS execution, check this box.
Use 7800 High Score Cart (7800 Emulation): For the 7800, there was a cartridge that provided a facility for 7800 games to save high score information. Not all games, however, took advantage of this. Set this checkbox to simulate this device—you will also need the associated ROM for this feature to work. EMU7800 will detect the ROM regardless of filename, as long as it is in the current ROM directory.

3.4.3 Console Tab

Console Tab

Events pertinate to the execution of the emulator are logged to the Console. Commands may also be issued here to access features not available via the GUI. To see what is available, enter ?.

3.4.4 Help Tab

Help Tab

The Help tab features an integrated web browser control. Two link controls are available, located at the bottom of the control. The README link references this README file on the local system. The Game Help link varies dependent upon the currently selected game, and is intended to reference original game instruction manuals, available online. At the time of this writing, not all games have help URLs defined. URLs can be specified in the ROMProperties.csv file, and more will be included in subsequent EMU7800 verisons. Standard web browser features, like the Back button and Refresh, are available by right-clicking in the browser window.

Note that when the Game Help link is clicked, it will "disable" to indicate the page is loading. It will "re-enable" once loading is complete. If no Game Help URL is available, the link will not be visible.

3.5 Addressing Performance Problems

In essence, EMU7800 is a streaming media application. Video output is a sequence of pixels emulating the television raster beam sweeping across the inside surface of the television screen. Similarly, audio output is a stream of pulses. The emulator operates by running as fast as possible, working to fill up the sound queue. Once full, the emulator waits on the queue until a sound frame opens up to receive the next frame of data. The sound queue is consumed by the audio device, at the necessary playback speed. This has the effect of opening up sound frames precisely at the desired frame rate and ultimately synchronizing the video and audio output together.

Should the sound queue be consumed at a faster rate than it can be filled, popping or buzzing noises will occur. The Settings Tab permit the frame rate to be throttled up or down from the default. Reducing the frame rate will reduce the rate at which the sound queue is consumed, giving the emulator a better chance of keeping up on slower machines.

3.6 External Command-line Options

To support various emulator front-end programs, EMU7800 can be launched with a full filename provided as a command-line argument:

EMU7800.exe "c:\Program Files\EMU7800\roms\OYSTR29.BIN"

Should the ROM file not be found, be unreadable, or not recognized, the GUI interface will be launched as normal. Clicking on the Console Tab will show the reason for the failure. Otherwise, the ROM will be run immediately.