antonblanchard / microwatt, Hacker News

A tiny Open POWER ISA softcore written in VHDL 2008. It aims to be simple and easy to understand.

Simulation using ghdl

• Build micropython. If you aren’t building on a ppc 64 le box you will need a cross compiler. If it isn’t available on your distro grab the powerpc 64 le-power8 toolchain fromhttps: / /toolchains.bootlin.com

git clone https://github.com/mikey/micropython cd micropython git checkout powerpc cd ports / powerpc make -j $ (nproc) cd ../../../

• Microwatt uses ghdl for simulation. Either install this from your distro or build it. Next build microwatt:

git clone https://github.com/antonblanchard/microwatt cd microwatt make

• Link in the micropython image:

ln -s ../micropython/ports/powerpc/build/firmware.bin simple_ram_behavioural.bin

• Now run microwatt, sending debug output to / dev / null:

./ core_tb>/ dev / null

Synthesis on Xilinx FPGAs using Vivado

• Install Vivado (I’m using the free 2019 .1 webpack edition).

• Setup Vivado paths:

source / opt / Xilinx / Vivado / 2019 .1 / settings 64 .sh

• Install FuseSoC:

pip3 install --user -U fusesoc

• Create a working directory and point FuseSoC at microwatt:

mkdir microwatt-fusesoc cd microwatt-fusesoc fusesoc library add microwatt / path / to / microwatt /

• Build using FuseSoC. For hello world (Replace nexys_video with your FPGA board):

fusesoc run --target=nexys_video microwatt --memory_size=8192 --ram_init_file=/ path / to / microwatt / fpga / hello_world.hex

• To build micropython (currently requires 1MB of BRAM eg an Artix-7 A 200):

fusesoc run --target=nexys_video microwatt

Testing

• A simple test suite containing random execution test cases and a couple of micropython test cases can be run with:

make -j $ (nproc) check

(Issues)

This is functional, but very simple. We still have quite a lot to do:

• Need to implement a simple non pipelined divide
• There are a few instructions still to be implemented
• Need to add caches and bypassing (in progress)
• Need to add supervisor state (in progress)