The simulator of project muir's two machines: QUUX, the CADR evolved, and the MIT CADR Lisp Machine itself, down to the chips.
The CADR is the second-generation MIT Lisp Machine, designed around 1978 by
Tom Knight, David Moon, Jack Holloway and Guy Steele. muir-sim models it far
enough down that the software written for the hardware runs --- the MIT
diagnostics, the console program CC, and two machines lashed together with
one debugging the other. That lashup is the acceptance test, and it passes.
QUUX is the same processor, buses and boards, changed where a change pays
for itself, and runs muir-sys's system for it; QUUX says
where it differs. There are three engines: micro, the fastest, with no
timing model; rtl, on the machine's own clock, for ordinary use; and
chip, which runs MIT's own drawings part by part, for the CADR. Rust, no
crate dependencies.
The site is muir.metebalci.com/simulator/, and the manual is the rest.
Install rustup, then open a new shell so cargo is on the path:
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
Build muir-sim and fetch QUUX's system. Until
muir-sys releases System 2002,
it is muir-sys's hand-over of it, the pre-release handover-2002-2999694.
The compiler version is pinned in rust-toolchain.toml, and the
hand-over lands in ref/band-2002-2999694/, every file checked against its
SHA-256 sum.
git clone https://github.com/metebalci/muir-sim
cd muir-sim
cargo build --release
tools/fetch-handover-2002.sh
QUUX reads its files from a host folder through a device of its own, so it needs no file server. Make the folder from the hand-over's sources, with an empty home to log in to, and start the machine:
mkdir -p ref/run
tar xzf ref/band-2002-2999694/handover-2002-2999694-sys.tar.gz -C ref/run
mkdir -p ref/run/release-2002-2999694/home/lispm
cp ref/band-2002-2999694/handover-2002-2999694-disk.vhd ref/run/disk.vhd
target/release/quux --micro --disk-pack ref/run/disk.vhd \
--file-root ref/run/release-2002-2999694
It says where its terminal is and boots. Point any VNC viewer at
vnc://127.0.0.1:5900, with no password: the display, keyboard and mouse
are the machine's way in. It boots to a Lisp Listener, System 2002;
(login "LISPM" "FILES" t) logs in. --micro is the faster engine;
without it quux runs rtl, at the machine's own speed.
System 2001, muir-sys's release for QUUX's hardware revision 13, runs on
muir-sim's tag quux-revisions-13-15, whose README says how.
The CADR is the reference: MIT's machine as built, running MIT's last release, System 100. Fetch it:
tools/fetch-system-100-for-cadr.sh
A Lisp Machine took its files and the date from a host on the Chaosnet, and a CADR had no such server in it, so muir-sim has none either. ozd is that host. Build it beside muir-sim and start it in a shell of its own, serving System 100's sources:
git clone https://github.com/metebalci/ozd ../ozd
(cd ../ozd && cargo build --release)
mkdir -p vendor/run/oz/lispm
../ozd/target/release/ozd --address 3060 --name MIT-OZ,OZ,system=UNIX \
--root $PWD/vendor/run/oz --root tree=$PWD/vendor/system-100-0/sys,ro \
--file-dates mit --timezone 5
--file-dates mit --timezone 5 has ozd give a file's dates as System 100
writes them, in its site's zone, 5 hours west of Greenwich
(sys/site/site.lisp:99, (:TIMEZONE 5)). ozd's default, plain UTC, is
for System 1002 and later, and a band of System 100 read through it has
every file date off by that zone.
Then start the machine. System 100's host table puts the machine at 3050 and its host at 3060; ozd has UDP port 42042, so the machine takes 42043.
target/release/cadr --disk-pack vendor/run/disk-sys-100-0.img \
--chaos-address 3050 --chaos-udp 42043 --chaos-udp-peer 3060@127.0.0.1:42042
It says where its terminal is and boots, on the same VNC terminal. In under
a minute it is at a Lisp Listener with the date set. Type (si:setup-cpt)
there for the mouse, which the terminal
explains, along with what to type when a boot with no host stops to ask for
the date.
muir-sys also evolves a system for the CADR, on the CADR's own line of
releases: tools/fetch-system-for-cadr.sh fetches its current one, and its
release notes give the ozd and cadr commands.
| QUUX | Where QUUX differs from the CADR, and what each difference needed of the boot PROM, the microcode and the system |
| The manual | Running muir-sim: what a run says, every flag, flags in a file, the prompt, the terminal, what a run can write, the Chaosnet and the two-machine lashup |
| Making a pack | diskpack, the third binary: a pack of one's own, its partitions, and bands loaded and dumped |
| How the engines work | micro, rtl and chip: what each computes, how fast each runs, and what each models board by board |
| The machine it models | The processor, the bus interface, the two buses and every board on them |
| Where the netlists come from | MIT's drawings and wire lists, how a board becomes a netlist, and what each is checked against |
| The Chaosnet board | The interface on the I/O board, its cable, and what muir-sim has of it |
| The TV board | The SIMPLE TV, the LISPM TV and the color TV |
| The keyboard boot sequence | The chord that boots the machine, from the keyboard's firmware to the processor |
| Sources and attribution | What this is built on, related projects, how it was written, and the license |
mit/ MIT's own files, unmodified: the drawings and wire lists of
every board modeled here, and a snapshot of System 100's own
sys tree, which the boot PROM comes from. mit/README.md
data/ what is made from mit/ by a script in tools/, each
cross-checked or labeled: the eight netlists, the disk
controller's microcode, the cable tables. data/README.md
src/ the simulator, its two executables cadr and quux, and
diskpack
tests/ the checks
examples/ development tools; none is part of the simulator.
examples/README.md
tools/ fetching the releases, and one script per board to
re-extract a netlist. tools/README.md
docs/ the manual, and findings about the machine read from mit/,
each claim cited to its file and held by a test where one
can. docs/README.md
vendor/ fetched material, never committed
Copyright (C) 2026 Mete Balci. Free software under the GNU Affero General
Public License, version 3 or, at your option, any later version; see
LICENSE. mit/ is MIT's work and tools/soap4/ came from ams/cadr4:
the license says what is whose.
muir-sim is implemented entirely by Claude Code, on Anthropic's Opus and Fable models.