A (free) open-source N64 development toolchain.
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README.md

n64chain

This is a Nintendo 64 development toolchain based on GCC that does not depend on any proprietary Nintendo library. Only thing that you need to provide is a 2kb bootcode compatible with your CIC to bootstrap the code. This is not included in n64chain.

The library includes basic OS functionality supporting multi-threading through hardware interrupts on the single MIPS 4300 CPU of the N64. Mainly written in C and MIPS assembly, it is expected to provide a lightweight development environment and thus requires some low-level baby sitting.

Building

To build the toolchain, first put your boot code named header.bin on the libn64 folder. Run build-posix64-toolchain.sh in the tools folder on a bash-compatible shell to start building the cross-compiler. Prerequisites are GMP, MPFR and MPC with development headers, build-essential, and bison, which can be installed via apt install build-essential libmpfr-dev libmpc-dev libgmp-dev flex bison on Ubuntu. On Mac, the Xcode command-line tools are also required. The other prerequisites can be installed via the homebrew package manager like so brew install mpfr isl libmpc gmp flex bison && brew link bison --force.

There is also a Windows compatible version build-win64-toolchain.sh that still requires a UNIX-like environment to run.

After the custom GCC build is completed, you should be able to build the helloworld example by running make inside helloworld folder or with make -C helloworld on project root. This will also build the libn64 dependency on the project root. When it is complete you should have a .z64 rom image ready to be run on a Nintendo 64. The same procedure applies for the rdpdemo and threadtest examples.

Basic N64 architecture

The N64 have a main MIPS4300 processor and a MIPS-like coprocessor called the Reality Co-processor (RCP). These two share the RDMEM, albeit not sharing a common data bus (instead through DMA controllers and instructions). RCP has two major sub-units namely the Reality Signal Processor (RSP) and Reality Display Processor (RDP).

Although use-case is dependent on the developer RSP, having an additional vector co-processor, is generally used for processing 3D transformations and audio processing via microcodes (a program written with a subset of MIPS instructions) and RDP is used for rasterizing the final image directly onto a display buffer. The latter uses custom 64-bit 'commands' that instruct RDP to do various pixel manipulations. Using these resources in a balance is key to write performant applications on N64.