Raven is an independent re-implementation of the Uxn CPU and Varvara Ordinator.

For details, see the project writeup.

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The raven-uxn crate includes three backends for Uxn CPU emulation:

• The baseline interpreter is a #[no_std] crate written in 100% safe Rust, with a single dependency (zerocopy). It is 10-20% faster than the reference implementation for CPU-heavy workloads (e.g. fib.tal, and mandelbrot.tal
• The unsafe ("native") interpreters are written in aarch64 and x86-64 assembly (with Rust shims on either side), and run significantly faster than the reference implementation (40-50% faster for AArch64, 2× faster for x86)
• The tailcall interpreter is also written in 100% safe Rust, but requires running a nightly toolchain. It is the fastest backend on AArch64, and faster than the baseline interpreter on x86-64 (but slower than the native assembly implementation)

Backends are feature-gated because they have platform and toolchain requirements; when making a desktop build, use --all-features to select all backends.

The native interpreter can be checked against the baseline interpreter with fuzz testing:

cargo install cargo-fuzz # this only needs to be run once
cargo +nightly fuzz run --release fuzz-native
# alternatively, run `just fuzz`

Performance can be tested with cargo bench, which runs Criterion.rs-based benchmarks for recursive Fibonacci computation and Mandelbrot fractal rendering.

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The Varvara implementation (raven-varvara) includes all peripherals, and has been tested on many of the flagship applications (Left, Orca, Noodle, Potato).

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The repository includes two applications built on these libraries:

• raven-cli is a command-line application to run console-based ROMs
• raven-gui is a full-fledged GUI, which runs both as a native application and on the web

Building the web application requires wasm-bindgen and wasm-opt to be installed. Using the Just command runner, the web application can be built with just dist (deploying files to raven-gui/dist) and served locally with just serve.

It's also possible to compile raven-cli as a WASM application (for use with wasmtime or similar):

rustup +nightly target add wasm32-wasip1
cargo +nightly build --release -praven-cli --target=wasm32-wasip1
# add `--features=tailcall` to test tailcall performance in WASM

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© 2024-2026 Matthew Keeter
Released under the Mozilla Public License 2.0

The repository includes ROMs compiled from the uxnemu reference implementation, which are © Devine Lu Linvega and released under the MIT license; see the roms/ subfolder for details.