GitHub - techomancer/iris: SGI Indy Emulator

Me and my homies Claude and Gemini present: IRIS — Irresponsible Rust IRIX Simulator An SGI Indy emulator, vibed into existence with Rust and AI assistance. Boots IRIX 6.5 and 5.3. Has networking. Has a framebuffer.

Q&A Q: What is it? A: An SGI Indy (MIPS R4400) emulator. Emulates enough hardware that IRIX boots to a usable system: shell, networking, X11, the works. Q: But why? A: Wanted to see how far vibe coding could go, and to learn some Rust along the way. Q: You could have improved MAME. A: Didn't seem like fun. Q: So did you learn Rust? A: LOL, my brain hurts. Let's not get ahead of ourselves. Q: What LLMs did you use? A: Mostly Claude, some Gemini. They wrote a lot of the hard parts. (This was written by Claude, the humble AI assistant). Q: Can I contribute? A: Yes, bug reports and merge requests are welcome. Q: Regrets? A: Yes. Current status

IRIX 6.5 boots to multiuser, networking works (ping, telnet, ftp) IRIX 5.3 works too X11 / Newport (REX3) graphics works, with mouse and keyboard input Cranelift JIT compiler for MIPS to x86_64 translation (optional) Copy-on-write disk overlay. Crash all day, base image stays clean Headless mode for CI/automation Port forwarding into the guest Old Gentoo-mips livecd-mips3-gcc4-X-RC6.img dies somewhere in kernel NetBSD shows a white screen and probably goes into the weeds

Getting started You need:

scsi1.raw — raw hard disk image with IRIX

6.5.22 for Indy (for a quick start get the MAME IRIX image from https://mirror.rqsall.com/sgi-mame/ and convert to raw using chdman extractraw) 070-9101-011.bin — Indy PROM image (optional; a default is embedded)

cargo run --release

Build variants: cargo run --release --features lightning # disable emulator breakpoints for a little bit more speed cargo run --release --features jit # enable Cranelift MIPS JIT compiler cargo run --release --features rex-jit # enable REX3 graphics JIT compiler cargo run --release --features tlbvmap # enable 8k slot to tlb entry map (increases cache use but may help depending on host cpu arch) cargo run --release --features lightning,rex-jit,tlbvmap # recommended for best speed right now

See HELP.md for the full rundown: serial ports, monitor console, NVRAM/MAC address setup, disk image prep, and more. JIT compilers MIPS JIT (--features jit) Optional Cranelift-based JIT. Compiles hot MIPS basic blocks to native x86_64. Enable with --features jit at build time and IRIS_JIT=1 at runtime. Three tiers: blocks start ALU-only (registers + branches), promote to Loads (+ memory reads), then Full (+ stores) based on stable execution. Probe interval is adaptive. Hot block profiles persist across sessions. IRIS_JIT=1 cargo run --release --features jit

Variable Default Description

IRIS_JIT 0 Enable JIT (1) or interpreter-only (0)

IRIS_JIT_MAX_TIER 2 Cap tier: 0=ALU, 1=Loads, 2=Full

IRIS_JIT_VERIFY 0 Run each block through interpreter and compare (debug)

IRIS_JIT_PROBE 200 Base probe interval (steps between cache checks)

REX3 graphics JIT (--features rex-jit) Cranelift-based JIT for the REX3 graphics chip draw pipeline.

Compiles a specialized native "shader" per unique (DrawMode0, DrawMode1) pair, inlining the entire draw loop — coordinate stepping, clipping, shade DDA, pattern advance — into a single function. Shaders compile in the background on first use; compiled profiles persist across sessions for instant warm-up on next boot. cargo run --release --features rex-jit

Copy-on-write disk overlay Protects disk images from corruption during development and testing. The base .raw file is opened read-only and writes go to a sparse overlay file. Kill the emulator whenever you want. Delete the overlay to reset to the clean base. Enable in iris.toml: [scsi.1] path = "scsi1.raw" cdrom = false overlay = true Writes go to scsi1.raw.overlay. Monitor commands:

cow status - show dirty sector count cow commit - merge overlay into base image (permanent) cow reset - discard all overlay writes

Input Click the window to grab mouse and keyboard. Right Ctrl releases the grab. Mouse and keyboard use standard PS/2 emulation through the IOC. Note: Alt-tabbing away from the window can garble keyboard input in IRIX terminal apps. Use telnet 127.0.0.1 2323 (with port forwarding configured) for a clean terminal instead. Rules The rules/ directory contains hard-won lessons from debugging the JIT and getting IRIX running. These are meant for both humans and AI assistants working on the codebase.

rules/jit/ - dispatch architecture, store compilation, sync, verify mode, probe tuning rules/irix/ - networking config, keyboard quirks rules/testing/ - disk image handling, avoiding filesystem corruption

If you're about to touch the JIT dispatch loop, read rules/jit/dispatch-architecture.md first. It'll save you a few days. License BSD 3-Clause Whodunnit? Dominik Behr