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https://github.com/JetSetIlly/Gopher2600

Gopher2600 is an emulator for the Atari 2600 games console
https://github.com/JetSetIlly/Gopher2600

atari2600 emulator emulator-development emulator-programming go golang-application

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Gopher2600 is an emulator for the Atari 2600 games console

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# Gopher2600



gopher2600 logo



Gopher2600 is an emulator for the Atari 2600 written in Go.



See here for [Current Status](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Current-Status)



Accuracy is very high and and there are no known problems with the emulation of the 6507, TIA or RIOT chips.



The key features of the emulator:



* [Support for many of the known cartridge formats](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Supported-Cartridge-Mappers)

    * emulation of the [Supercharger](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Supercharger) - supports loading from WAV files

* Emulation of the [ARM7TDMI](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/ATM7TDMI-Emulation) as found in the `Harmony` cartridge

	* Preliminary support for the ARMv7-M as used in the `UnoCart` and `PlusCart` is also included

* Network access through [PlusROM](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/PlusROM) emulation

* [AtariVox and SaveKey](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/AtariVox-and-SaveKey) support

    * Speech support via `Festival`

* CRT TV Effects

* Flexible [screenshot](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Creating-Screenshots) features

* Accurate audio reproduction (and optional stereo output)

* Support for common [TIA revisions](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/TIA-Revisions)

* Implementation of [Movie Cart](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Movie-Cart)

* [Gameplay rewinding](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Rewinding)

* Tracker/Piano Keys visualisation

* [Gameplay recording and playback](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Recording-Gamplay)

* Support for (and auto-detection of) the stick, paddle, keypad and also Sega Genesis style [controllers](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Hand-Controllers-and-Front-Panel)

* ROM selector with live emulation preview and optional support for

  [boxart and the standard stella.pro file](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Box-Art-and-stella.pro-file)



The graphical [debugger](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Debugger):



* CPU and Color Clock level interaction

* Breakpoints, traps, watches on various CPU, TIA and RIOT targets

* Terminal interface (headless operation optional)

* Advanced ARM monitoring

	* Performance profiling

	* Source code inspection and breakpoints

	* DWARF support (global & local variable inspection)



Logo is based on [Gopherize.me](https://github.com/matryer/gopherize.me) which itself is based on the work of [Ashley McNamara](https://github.com/ashleymcnamara/gophers) and is [licensed under the Creative Commons](https://github.com/ashleymcnamara/gophers/blob/master/LICENSE).



## Documentation



User documentation for the emulator can be found in the [Gopher2600-Docs repository](https://github.com/JetSetIlly/Gopher2600-Docs/) and in particular the [live wiki](https://github.com/JetSetIlly/Gopher2600-Docs/wiki).



Development & Maintenance documentation can be found in the [Gopher2600-Dev-Docs repository](https://github.com/JetSetIlly/Gopher2600-Dev-Docs/). Also, source level documentation (for the most recent release) can be found on [go.dev](https://pkg.go.dev/github.com/jetsetilly/gopher2600).



## Example Screenshots



The following [screenshots](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/Creating-Screenshots) were taken in `playmode` with CRT effects enabled.



	

		

			pitfall

		

		

			chiphead

		

		

			thrust

		

	

	

		

			man goes down

		

		

			soul of the beast

		

		

			egypt genesis

		

	

	

		

			draconian

		

		

			zookeeper

		

	



ROMs shown: Pitfall; [Chiphead](https://www.pouet.net/prod.php?which=68505); Thrust; Man Goes Down; [Soul of the Beast](https://aeriform.itch.io/beast); [Egypt 2600BC](https://www.pouet.net/prod.php?which=72716) ; Draconian; [Zookeeper](https://champ.games/downloads)



## Resources used



The Stella project (https://stella-emu.github.io/) was used as a visual

reference for video output. In the absence of VCS hardware (which I didn't have

during initial TIA development) Stella was a good alternative for checking

the accuracy of video output.



In addition, Stella was used as reference in the following areas:



* During the development of the CDF cartridge formats. These recent formats don't

seem to be documented anywhere accept in the Stella source.



* Cartridge fingerprints for ParkerBros, Wickstead Design, SCABS, UA and JANE.



* As a reference for the audio implementation (the 6502.ts project was also

  referenced for this reason).



* Fingerprint patterns for automated controller/peripheral selection.



In all these instances, primary sources of information could not be found.



(Earlier revision of Gopher2600 used Stella a reference for the EF cartridge

format. However, the implementation has been vastly simplified by declaring EF

to be a nothing more than a 64k Atari ROM. The discussion that led to this

revelation can be found in the link below.)



https://forums.atariage.com/topic/346341-64ksc-multi-sprite-roms-error-out-in-stella-for-me/page/2/#comment-5188396



Many notes and clues from the AtariAge message boards. Most significantly the

following threads proved very useful indeed:



* "Cosmic Ark Star Field Revisited"

* "Properly model NUSIZ during player decode and draw"

* "Requesting help in improving TIA emulation in Stella" 

* "3F Bankswitching"

* "TIA Sounding Off in the Digital Domain"



And from and old mailing list:



* "Games that do bad things to HMOVE..." https://www.biglist.com/lists/stella/archives/199804/msg00198.html



These mailing lists and forums have supplied me with many useful test ROMs. I

aim to package these up and distribute them sometime in the future (assuming I

can get the required permissions).



Extensive references have been made to Andrew Towers' "Atari 2600 TIA Hardware

Notes v1.0"



Cartridge format information was found in Kevin Horton's "Cart Information

v6.0" file (sometimes named bankswitch_sizes.txt)



The WF8 format discussed here on AtariAge



https://forums.atariage.com/topic/367157-smurf-rescue-alternative-rom-with-wf8-bankswitch-format/



The "Stella Programmer's Guide" by Steve Wright is of course a key document,

used frequently throughout development.



Colour values for NTSC and PAL television signals taken from https://www.qotile.net/minidig/docs/tia_color.html



The TIA Audio implementation is based almost entirely on the work of Chris Brenner.



https://atariage.com/forums/topic/249865-tia-sounding-off-in-the-digital-domain/



Additional work on volume sampling a result of this thread:



https://forums.atariage.com/topic/370460-8-bit-digital-audio-from-2600/



Musical information as seen in the tracker window taken from Random Terrain.



https://www.randomterrain.com/atari-2600-memories-music-and-sound.html



The 6507 information was taken from Leventhal's "6502 Assembly Language

Programming" and the text file "64doc.txt" v1.0, by John West and Marko Makela.



Undocumented 650x instructions and implementation details in "6502/6510/8500/8502 Opcode matrix" 



http://www.oxyron.de/html/opcodes02.html



6502 functional tests from https://github.com/Klaus2m5/6502_65C02_functional_tests



US Patent Number 4,644,495 was referenced for the implementation of the DPC cartridge format

(the format used in Pitfall 2) https://patents.google.com/patent/US4644495/en



US patent 4,485,457A was used to help implement the CBS cartridge format

https://patents.google.com/patent/US4485457A/en



European patent 84300730.3 was used to help implement the SCABS cartridge format

https://worldwide.espacenet.com/patent/search/family/023848640/publication/EP0116455A2?q=84300730.3



DPC+ format implemented according to notes provided by Spiceware https://atariage.com/forums/topic/163495-harmony-dpc-programming and https://atariage.com/forums/blogs/entry/11811-dpcarm-part-6-dpc-cartridge-layout/



DPC+ARM information on Spiceware's blog https://atariage.com/forums/blogs/entry/11712-dpc-arm-development/?tab=comments#comment-27116



The "Mostly Inclusive Atari 2600 Mapper / Selected Hardware Document" (dated 03/04/12) by Kevin Horton



Supercharger information from the Kevin Horton document above and also the `sctech.txt` document



Reference for the ARM7TDMI-S, as used in the Harmony cartridge formats:



https://developer.arm.com/documentation/ddi0234/b



For detail about the Thumb instruction set the following document was

preferred. Mnemonics used in the ARM disassembly are from this document:



http://bear.ces.cwru.edu/eecs_382/ARM7-TDMI-manual-pt1.pdf



Further information from the ARM Architecture Reference Manual:



http://www.ecs.csun.edu/~smirzaei/docs/ece425/arm7tdmi_instruction_set_reference.pdf



https://www.cs.miami.edu/home/burt/learning/Csc521.141/Documents/arm_arm.pdf



Specific information about UXP ARM7TDMI-S 



https://www.nxp.com/docs/en/user-guide/UM10161.pdf



Thumb-2 information in the ARM Architecture Reference Manual Thumb-2 Supplement



https://documentation-service.arm.com/static/5f1066ca0daa596235e7e90a



and the "ARMv7-M Architecture Reference Manual" can be found at:



https://documentation-service.arm.com/static/606dc36485368c4c2b1bf62f



Specific information about the STM32F407 used in the UnoCart and PlusCart can

be found at:



https://www.st.com/resource/en/reference_manual/dm00031020-stm32f405-415-stm32f407-417-stm32f427-437-and-stm32f429-439-advanced-arm-based-32-bit-mcus-stmicroelectronics.pdf



In relation to ARM development, information about the DWARF format is being

taken from the DWARF2 and DWARF4 standards:



https://dwarfstd.org/doc/dwarf-2.0.0.pdf



https://dwarfstd.org/doc/DWARF4.pdf



ARM specific DWARF information taken from:



https://github.com/ARM-software/abi-aa/releases/download/2023Q1/aadwarf32.pdf



## Other Software / Libraries



The following projects are used in the `Gopher2600` project:



* https://github.com/ocornut/imgui

* https://github.com/inkyblackness/imgui-go

* https://github.com/veandco/go-sdl2

* https://github.com/go-gl/gl

* https://github.com/hajimehoshi/go-mp3

* https://github.com/pkg/term

* https://github.com/go-audio/wav

* https://github.com/sahilm/fuzzy



* FontAwesome

	* https://fontawesome.com/

	* licensed under the Font Awesome Free License

* Hack-Regular 

	* https://github.com/source-foundry/Hack

	* licensed under the MIT License

* JetBrainsMono

	* https://github.com/JetBrains/JetBrainsMono

	* licensed under the OFL-1.1 License



Both 6502.ts and Stella were used as reference for the Audio implementation.



Some ideas for the fragment shaders taken from:



* https://github.com/libretro/glsl-shaders/blob/master/crt/shaders/crt-pi.glsl

* https://www.shadertoy.com/view/ltB3zD

* https://github.com/mattiasgustavsson/crtview

* https://gist.github.com/Beefster09/7264303ee4b4b2086f372f1e70e8eddd



The Festival Speech Synthesis System is an optional program that can be run

alongside the emulator for [AtariVox](https://github.com/JetSetIlly/Gopher2600-Docs/wiki/AtariVox-and-SaveKey) support



http://www.festvox.org/docs/manual-2.4.0/festival_toc.html



## Personal Thanks and Acknowledgements



At various times during the development of this project, the following people

have provided advice and encouragement: Andrew Rice, David Kelly. And those

from AtariAge who have provided testing, advice and most importantly,

encouragement (alphabetically): alex_79; Al Nafuur; Andrew Davie; Batari;

DirtyHairy; John Champeau; MarcoJ; MrSQL; Rob Bairos; Spiceware; Thomas

Jenztsch; Zachary Scolaro; ZeroPageHomebrew