GaZmusino. A tiny open source RISC-V processor

This project is an open-source implementation of a rv32i_zmmul_zicsr RISC-V processor, designed for learning and experimentation developed in the GaZ research group.

Features

• RISC-V ISA Compliance: Supports the rv32i_zmmul_zicsr instruction set.
• Modular Design: Easily extendable with additional functional units.
• Memory Options: Includes a C++ simulated RAM or a SystemVerilog-based implementation.
• Instruction Simulation: Enables C++ testbench-based instruction simulation.
• Flexible Build Tools: Python-based build module simplifies running ASM/C/C++ projects on the processor.
• Trace Visualization: Compatible with Konata for visualizing execution traces.
• Basic BSP Implementation: Provides a basic board support package (BSP) for static linking with libc.
• Automated Testing: Includes a suite of adapted RISC-V standard isa tests and the bringup-bench test collection.
• FPGA Compatibility: Synthesizable for deployment on Xilinx FPGAs. Tested on Zynq UltraScale+ ZCU104 Evaluation Board FPGA with a target clock frequency of 100 Mhz.

Cloning

The bringup-bench test collection is included as a submodule. To clone this repository, use:

git clone --recurse-submodules

Requirements

The following program versions have been verified to work. Other versions may not work as expected:

• Python 3.12.7
• Make 4.4.1
• GCC x86_64 14.2.1
• RISC-V GNU toolchain 13.2.0
• Verilator 5.024 2024-04-05

RISC-V GNU toolchain flags

The RISC-V GNU toolchain must be configured using the following flags:

./configure --enable-multilib --with-multilib-generator="rv32i_zmmul_zicsr-ilp32--"

Testing

To execute a basic set of tests and build the processor using Verilator, run:

make test

For a larger set of tests, run:

make bringup

Examples

The examples directory includes two "Hello World!" projects. These can be executed using the Python build.py module:

import build
# C++ Hello world project 
build.build_and_run("examples/cpp_hello_world", "build")
# C Hello world project
build.build_and_run("examples/c_hello_world", "build")

Both projects include libc startup code. For a baremetal project, use:

import build
build.build_and_run_bare("examples/bare", "build", "trace.trace", "trace.kanata")

Simulation outputs can include the stdout file, a YAML file containing profiling counters values, and a trace file that can be visualized using Konata.

import build
build_and_run_log("examples/c_hello_world", "build", "stdout.txt", "prof.yaml")