[libre-riscv-dev] KCP53000B micro-architecture thoughts

[Jacob Lifshay]

On Wed, May 29, 2019, 22:35 Samuel Falvo II <sam.falvo at gmail.com> wrote:

> Things to consider for the future perhaps; I'm just trying to build up
> an understanding and an implementation to test my understanding.  I'm
> seriously considering abandoning the 6502-style "one giant PLA to rule
> them all" decoder in favor of a *small* out-of-order approach, just to
> play with the ideas and confirm my understanding (one CSR-FU, one
> load/store unit which also does addition/subtraction, one logical unit
> to do XOR, AND, etc., and one branch unit to deal with JAL, JALR, and
> the conditional branches).  Then, after that, I was thinking of going
> back to re-read Thornton and Mitch Alsup's chapters with my design
> experience helping to inform my understanding and learn some of the
> finer details.
>
I'd recommend having the additional add/sub unit combined with the branch
unit since all compares are sub & check top 2 bits of result & check carry
out & check if result (without carry out) is zero.

Jacob