7 ms·

Nice one! Sounds like a fun project to do. Did you follow any tutorial or guide for this? If so, I would appreciate it if you shared it.

• Flex247A 2mo ago
  Hi, I didn't follow any specific guide on this, but asked ChatGPT about the bare minimum environment needed to run DOOM. From there, I figured out how to execute the instructions using a switch-case and how to make a custom syscall to trigger rendering. I made a post a while back that details the entire process: https://www.reddit.com/r/EmuDev/comments/1t1or4j/doom_runs_on_my_custom_riscv_emulator/ https://www.reddit.com/r/EmuDev/comments/1t1or4j/doom_runs_o...
  • kailpa1 2mo ago
    Thanks, am going to check it out.
• sph 2mo ago
  If you don't want to delegate the fun of learning to an LLM, here's how I've built a RV64IM simulator in C in a weekend. All you need is an opcode table, the RISC-V specs and to implement each instruction; the good thing of RISC CPUs is that instructions are very simple (i.e. pretty much everything is a variation of `dest = src1 OP src2`) and memory instructions are dedicated. The other cool thing is that there are no "flags". Start with the base instruction set, then you can add M on top later. 64-bit support requires just a handful more instructions to zero/sign extend from 32-bit. Then, wire your simulator to https://github.com/riscv-software-src/riscv-tests https://github.com/riscv-software-src/riscv-tests, and there you have an official test suite. When everything passes, you have a fully-compliant RISC-V CPU. You can at this point tell GCC or Rust or your favourite language to compile to RV32IM and see it run on your simulator. It's a very gratifying process. If you get at this stage, you might want to use the ecall instruction to hard-code I/O operations such as "read from stdin" or "print a character", and there you have a sandboxed CPU that you can target with your favourite programming language. Make it run DOOM (start with https://github.com/ozkl/doomgeneric https://github.com/ozkl/doomgeneric and see which I/O do you need), or turn it into a toy game console; the sky's the limit. --- Here's a copy-paste of the list of resources I have saved in my notes: - https://github.com/libriscv/libriscv https://github.com/libriscv/libriscv A very fast RISC-V VM with sandboxing of memory and syscalls. - https://luplab.gitlab.io/rvcodecjs/ https://luplab.gitlab.io/rvcodecjs/ RISC-V Instruction Encoder/Decoder - https://www.cs.sfu.ca/~ashriram/Courses/CS295/assets/notebooks/RISCV/RISCV_CARD.pdf https://www.cs.sfu.ca/~ashriram/Courses/CS295/assets/noteboo... Reference card - https://cs.brown.edu/courses/csci1952y/2024/assets/docs/riscv-spec-v2.2.pdf https://cs.brown.edu/courses/csci1952y/2024/assets/docs/risc... Spec - https://riscv-software-src.github.io/riscv-unified-db/manual/html/isa/isa_20240411/insts/sd.html https://riscv-software-src.github.io/riscv-unified-db/manual... - ABI: https://lists.riscv.org/g/tech-psabi/attachment/61/0/riscv-abi.pdf https://lists.riscv.org/g/tech-psabi/attachment/61/0/riscv-a... Good luck!
  • kailpa1 2mo ago
    Huge thanks! Will certainly try doing that.