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Steampunk

CI

Because what the world needs right now is yet another retro computing emulator. So yeah, here it is. This started as a "father and son" hobby project. It's built with no particular agenda other than having fun (and learning Rust). Currently, the project contains an Atari 2600 emulator based on a cycle-based 6502 implementation, as well as some humble beginnings of a Commodore 64 emulator.

Installing requirements

Rust

The emulator is built in Rust, so obviously, first you need to install the Rust toolchain. At the moment of writing this document, a nightly version of Rust is required:

rustup install nightly
rustup default nightly

Development libraries

Depending on your system, you may need to install the following libraries to build Steampunk:

  • libasound2-dev
  • libsdl2-dev

cc65

One important dependency is a cc65 compiler. Technically, we only rely on its 6502 assembler, but it comes in a bigger package. We also only use it for tests, so it could be probably skipped for a regular build, but we are lazy.

  • On Mac, it's enough to say brew install cc65, provided that you already have Homebrew installed.
  • On Windows, it's a bit more involved, unsurprisingly. You first need to download and unpack the Windows snapshot of cc65 to a directory of your choice. Next, you need to add the bin directory of cc65 to the system PATH variable. Here is a nice tutorial if you don't know how to do it.
  • On Linux, refer to this page. Note that the latest Debian packages should work on Ubuntu (they are used in this project's CI build).

Atari 2600 emulator

Building and running

Assuming that both Rust and cc65 are properly installed, simply run the following command:

cargo run --release --bin=atari2600 -- <rom-file-path>

Where <rom-file-path> is a path of the Atari 2600 ROM to be executed. Make sure to run the optimized binary (--release); the debug one is way too slow.

Keyboard mapping

  • 1: Toggle TV type switch
  • 2: Toggle player 1 difficulty
  • 3: Toggle player 2 difficulty
  • 4: Game select
  • 5: Game reset
  • W, A, S, D, Left Shift, Space: Player 1 Joystick
  • I, J, K, L, N, ., arrow keys: Player 2 Joystick

Compatibility

Currently, the following official Atari 2600 cartridges are known to be supported:

  • Basic Math, a.k.a. Fun with Numbers
  • Combat
  • Air-Sea Battle
  • Starship… sort of. For some reason, we are unable to aim down.
  • Surround

Commodore 64 emulator

The C64 emulator is so far capable of running simple BASIC programs and loading stuff from TAP files, but it's still in a very early stage of development. To run it, use a following command:

cargo run --bin=c64 --release

As in the Atari 2600 case, it's important to use the release build. Actually, it's even more important; since C64 is more complicated, the debug build crawls like a stoned snail.

In order to use a TAP file, you need to specify its path while starting the emulator (no tape switching supported just yet):

cargo run --bin=c64 --release -- --tape=<tape_path>

Then, while the emulator is running, press ⌘P (or ⊞P, depending on the system) to press Play.

Debugging

One nice feature that helps development is ability to attach VS Code debugger to debug the emulated 6502 code. If you ever wanted to use a 2020s toolchain to debug 1970s technology, well, look no further. Using the Steampunk 6502 debugger extension, you can debug 6502 assembly code on both Atari 2600 and C64. Please refer to the debugger extension's documentation for detailed usage instructions.

Note that it's still recommended to use a release build of Steampunk for 6502 debugging; this feature doesn't depend on debugging the emulator code itself.

Known issues and limitations

  • Unofficial 6502 opcodes are not supported
  • No support for bank switching (Atari 2600)
  • No support for input devices other than joysticks (Atari 2600)
  • Can't press the Stop button on Datasette just yet. YOLO.