[libre-riscv-dev] next tasks

Jacob Lifshay programmerjake at gmail.com
Thu Feb 20 07:55:59 GMT 2020

On Wed, Feb 19, 2020, 23:34 Lauri Kasanen <cand at gmx.com> wrote:

> However may I suggest the POWER MicroWatt core?
> https://github.com/antonblanchard/microwatt
> Open license, written in VHDL, rough complexity when compiled for a
> fpga 11k luts, 4k ffs.

I think that could work out really well, being Power ISA and 64-bit,
however MicroWatt doesn't implement all of the Power instructions yet, as
well as potentially having other things that will need to be implemented.

One issue we may have is that I'm not sure if yosys can read VHDL, I know
it wasn't able to before.

It doesn't matter much what arch the boot processor is, whatever is
> freely and easily available. Could be Z80 or 6502 even.

It's not necessarily just a boot processor, it can also be used for
bit-banging peripherals (the main cores aren't designed for consistent
timing due to caches & stuff) and things like power management where you
need it to keep running even if you turn off (as in power supply turned
off) the main processors while sleeping. Also, having a really low-power
core be able to keep running even if the chip is overheating is useful to
be able to re-enable stuff once it cools down again.


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