A tiny Open POWER ISA softcore written in VHDL 2008

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common.vhdl	More second write port removal	5 years ago
core.vhdl	Move wishbone arbiter out of the core	5 years ago
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cr_file.vhdl	Fix CR forwarding	5 years ago
crhelpers.vhdl	Initial import of microwatt	5 years ago
decode1.vhdl	Add a decode bit to mark an instruction as single through the pipeline	5 years ago
decode2.vhdl	Merge pull request #25 from antonblanchard/register_file_printing	5 years ago
decode_types.vhdl	Add a decode bit to mark an instruction as single through the pipeline	5 years ago
execute1.vhdl	Remove dynamic ranges from code	5 years ago
execute2.vhdl	Initial import of microwatt	5 years ago
fetch1.vhdl	Initial import of microwatt	5 years ago
fetch2.vhdl	Initial import of microwatt	5 years ago
glibc_random.vhdl	Initial import of microwatt	5 years ago
glibc_random_helpers.vhdl	Initial import of microwatt	5 years ago
helpers.vhdl	Remove dynamic ranges from code	5 years ago
insn_helpers.vhdl	Rework decode2	5 years ago
loadstore1.vhdl	Remove some more loadstore debug	5 years ago
loadstore2.vhdl	Remove second write port	5 years ago
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multiply.vhdl	Quieten multiply warning	5 years ago
multiply_tb.vhdl	Initial import of microwatt	5 years ago
ppc_fx_insns.vhdl	Remove dynamic ranges from code	5 years ago
register_file.vhdl	Add forwarding in the register file	5 years ago
sim_console.vhdl	Initial import of microwatt	5 years ago
sim_console_c.c	Make sim poll non-blocking	5 years ago
sim_uart.vhdl	Share soc.vhdl between FPGA and sim	5 years ago
simple_ram_behavioural.vhdl	Share soc.vhdl between FPGA and sim	5 years ago
simple_ram_behavioural_helpers.vhdl	Initial import of microwatt	5 years ago
simple_ram_behavioural_helpers_c.c	Silence some loadstore related debug	5 years ago
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soc.vhdl	Switch soc to use std_ulogic	5 years ago
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wishbone_types.vhdl	Initial import of microwatt	5 years ago
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README.md

Microwatt

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

Simulation using ghdl

MicroPython running on Microwatt

Build micropython. If you aren't building on a ppc64le box you will need a cross compiler. If it isn't available on your distro grab the powerpc64le-power8 toolchain from https://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/settings64.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 A200):

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)