Implementing a CHIP-8 Emulator
Writing a simple emulator from scratch is fun: rCHIP8
I’ve written about the CHIP-8 machine before. It is a very simple interpreted programming language that can be implemented without much hassle by anyone interested in getting their feet wet with emulators. It is commonly regarded as the “hello world” of emulators.
Some time ago I decided to implement a CHIP-8 emulator in Rust as my second project written in that language. My first foray into the language was the porting of the Gaia Sky LOD catalog generation tool from Java. This allowed us to substantially increase the generation speed and dramatically (really) decrease the memory consumption of the processing, to the point where a processing that previously needed more than 2 TB of RAM could now be done with less than a hundred gigs. Back to the topic at hand, I called my implementation
rchip8 (very creative). This post describes the process and structure of such an emulator with more or less detail.
Looking for new projects to sharpen my Rust skills, I came across a Reddit post where someone mentioned CHIP-8. CHIP-8 is an interpreted low-level programming language and virtual machine specification that is very commonly used as a “Hello world!” project of sorts for people to get their feet wet with emulator programming. It is simple enough to be able to implement a fully-featured emulator in a couple of sessions, but it has all the key parts of a real machine, to the point that are many projects that implement CHIP-8 directly in hardware.
I have since implemented my own CHIP-8 emulator in Rust (see repository here) with support for sound, display scaling, configurable colors, and more. But this text is not about it (I’ll write about my implementation in a future post). Today I want to fully describe the CHIP-8 machine, because I had fun implementing it, and I like it so much that I want to have it here for my future reference. In this guide, every instruction is accompanied with a small pseudo-code block to help understand the interpreter’s intended behavior to the more technically inclined reader.
The CHIP-8 specification document I used as reference to implement my version is Cowgod’s Chip-8 technical reference1, and I also had a look at a guide by Tobias V. Langhoff.2