This repository hosts an assembler, an emulator and a couple of test programs for a fictitious CPU architecture designed to minimize exchanges between CPU and memory, presented at COMPAS 2018:
Florent de Dinechin, Maxime Darrin, Antonin Dudermel, Sébastien Michelland, Alban Reynaud. Une architecture minimisant les échanges entre processeur et mémoire. ComPAS 2018 - Conférence d’informatique en Parallélisme, Architecture et Système, Jul 2018, Toulouse, France. pp.1-8. ⟨hal-01959855⟩
The emulator has some debugger functions, and can be seen below running the main example application, a nested CHIP-8 emulator:
This project was the result of an architecture class at ENS de Lyon, and was inflicted upon the teachers of the compilers class the following year.
The architecture is mostly described in the conference paper and in
subject/isa2017v2.pdf (both in French). The main
idea is to have a fairly reduced instruction set, and to reduce the size of
instructions to a minimum in order to obtain the most compact encoding
possible.
Byte-level granularity is somewhat unsatisfying for the most common intructions so everything is at the bit-level instead; even the memory is bit-addressable.
Most instructions use Huffman coding to reduce the size of the instruction when the operands are small. The instructions themselves are encoded using a Huffman scheme based on statistics collected early on during the project.
There are 8 general-purpose registers and 2 pointer registers (called "counters"). The default addressing mode is auto-increment; it's also the only addressing mode, which is an obvious mistake IMHO.
The doc folder contains some informations on the calling conventions. In
particular, doc/remarks_fr.txt contains some of the
finer analysis (in French).
Type make to assemble the example programs, build the emulator and assemble
the CHIP-8 emulator. The emulator requires ncurses. See
doc/emu_troubleshooting.md for some common
problems.
The assembler is in the compiler folder. It's a joint work with minimal
planning so the source is a little bit rough.
This repository comes with possibly the least efficient CHIP-8 emulator out there, running unoptimized assembler code through the emulator of a fictitious, not particularly efficient architecture.
Use ./chip8_play.sh <GAME> to play a CHIP-8 game. The list of cartridges is
in the chip8/GAMES folder. I might suggest:
% ./chip8_play.sh BRIX
To reproduce the screenshot above, change -r into -d in chip8_play.sh.