microwatt

A tiny Open POWER ISA softcore written in VHDL 2008

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Paul Mackerras 2167186b5f Make multiplier hang off the side of execute1 With this, the multiplier isn't a separate pipe that decode2 issues instructions to, but rather is a unit that execute1 sends operands to and which sends the result back to execute1, which then sends it to writeback. Execute1 now sends a stall signal when it gets a multiply instruction until it gets a valid signal back from the multiplier. This all means that we no longer need to mark the multiply instructions as single-issue. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>		5 years ago
fpga	Fix some ghdlsynth issues with fpga_bram	5 years ago
hello_world	Move bin2hex.py to scripts/	5 years ago
media	…
scripts	Move bin2hex.py to scripts/	5 years ago
sim-unisim	…
tests	Dump CTR, LR and CR on sim termination, and update our tests	5 years ago
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LICENSE	…
Makefile	Make multiplier hang off the side of execute1	5 years ago
README.md	…
cache_ram.vhdl	…
common.vhdl	Make multiplier hang off the side of execute1	5 years ago
control.vhdl	…
core.vhdl	Make multiplier hang off the side of execute1	5 years ago
core_debug.vhdl	…
core_tb.vhdl	…
countzero.vhdl	…
countzero_tb.vhdl	…
cr_file.vhdl	Dump CTR, LR and CR on sim termination, and update our tests	5 years ago
cr_hazard.vhdl	…
crhelpers.vhdl	…
dcache.vhdl	…
dcache_tb.vhdl	…
decode1.vhdl	Make multiplier hang off the side of execute1	5 years ago
decode2.vhdl	Make multiplier hang off the side of execute1	5 years ago
decode_types.vhdl	Make multiplier hang off the side of execute1	5 years ago
divider.vhdl	Remove unused signal	5 years ago
divider_tb.vhdl	…
dmi_dtm_dummy.vhdl	…
dmi_dtm_tb.vhdl	…
dmi_dtm_xilinx.vhdl	…
execute1.vhdl	Make multiplier hang off the side of execute1	5 years ago
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fetch2.vhdl	…
glibc_random.vhdl	…
glibc_random_helpers.vhdl	…
gpr_hazard.vhdl	…
helpers.vhdl	…
icache.vhdl	Fix a ghdlsynth issue in icache	5 years ago
icache_tb.vhdl	…
icache_test.bin	…
insn_helpers.vhdl	…
loadstore1.vhdl	…
logical.vhdl	…
microwatt.core	…
multiply.vhdl	Make multiplier hang off the side of execute1	5 years ago
multiply_tb.vhdl	Make multiplier hang off the side of execute1	5 years ago
plru.vhdl	…
plru_tb.vhdl	…
ppc_fx_insns.vhdl	…
register_file.vhdl	Fix ghdlsynth issue in register file	5 years ago
rotator.vhdl	…
rotator_tb.vhdl	…
sim_bram.vhdl	…
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sim_bram_helpers_c.c	…
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sim_uart.vhdl	…
soc.vhdl	Removed unused core_terminated signal	5 years ago
utils.vhdl	…
wishbone_arbiter.vhdl	…
wishbone_bram_tb.bin	…
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wishbone_bram_wrapper.vhdl	…
wishbone_debug_master.vhdl	…
wishbone_types.vhdl	…
writeback.vhdl	Make multiplier hang off the side of execute1	5 years ago

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

You can try out Microwatt/Micropython without hardware by using the ghdl simulator. If you want to build directly for a hardware target board, see below.

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/micropython/micropython.git
cd micropython
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 main_ram.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

Fedora users can get FuseSoC package via

sudo dnf copr enable sharkcz/danny
sudo dnf install 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 such as --target=arty_a7-100):

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

You should then be able to see output via the serial port of the board (/dev/ttyUSB1, 115200 for example assuming standard clock speeds). There is a know bug where initial output may not be sent - try the reset (not programming button on your board if you don't see anything.

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:

There are a few instructions still to be implemented
Need to add caches and bypassing (in progress)
Need to add supervisor state (in progress)