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Running Doom on Our Custom CPU and Going Viral

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Re: Running Doom on Our Custom CPU and Going Viral

#21

Post by kailpa1 »

sph wrote: post #17
kailpa1 wrote: post #10

Earlier quoted context omitted.

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.

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 n…

Huge thanks! Will certainly try doing that.

Re: Running Doom on Our Custom CPU and Going Viral

#22

Post by kailpa1 »

Flex247A wrote: post #13
kailpa1 wrote: post #10

Earlier quoted context omitted.

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.

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_o...

Thanks, am going to check it out.

Re: Running Doom on Our Custom CPU and Going Viral

#24

Post by _joel »

Cool, I thought this was a CPU custom designed for Doom, but I guess that's just a 486 :)

edit: I went to down a quick hole "The historical footnote is that a version of this genuinely happened. SNES Doom shipped with a Super FX 2 in the cartridge, a custom RISC chip with a pixel-plot instruction, because the console's own CPU had no chance. Jaguar and PlayStation ports both moved the rasteriser onto dedicated hardware. Doom's design was shaped by the absence of an FPU, and then hardware kept getting built to catch up with it."

Re: Running Doom on Our Custom CPU and Going Viral

#25

Post by arghunter »

terekhindc wrote: post #15

why Zmmul and not full M — is it just fpga area, or did the doom port let you drop div/rem?

I'm kinda lazy lol. We are also implementing out-of-order rn, so we want to get a really solid rv32i setup going before adding multiplication, floating point, vector, etc.

Re: Running Doom on Our Custom CPU and Going Viral

#28

Post by blastonico »

_joel wrote: post #24

Cool, I thought this was a CPU custom designed for Doom, but I guess that's just a 486 :) edit: I went to down a quick hole "The historical footnote is that a version of this genuinely happened. SNES Doom shipped with a Super FX 2 in the cartridge, a custom RISC chip with a pixel-plot instruction, because the console's own CPU had no chance. Jaguar and PlayStation ports both moved the rasteriser onto dedicated hardwa…

> but I guess that's just a 486

*just* a 486. :-(

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