Porting Xv6 to a Homebuilt CPU

A student project at University of Tokyo designed a custom RISC CPU on FPGA and built a homegrown C compiler from scratch.

A joint team (Group X) aimed to port MIT’s educational Unix-like OS Xv6 onto their custom CPU, requiring new toolchain and CPU features.

They created Ucc, a C89 compiler in OCaml, and enhanced their simulator to support interrupts and virtual memory with hardware page walking.

Porting challenges included low portability of Xv6, data type size mismatches, and cache alias issues, solved by making char 8-bit and using page coloring.

After implementing interrupts, MMU, and simulator debug features, Xv6 booted on the simulator and real CPU, running interactive apps like sl, minesweeper, and 2048.

They culminated by running the original ray-tracing program atop Xv6 on their custom CPU, showcasing full software stack functionality.