[Libre-soc-dev] svp64 review and "FlexiVec" alternative

[Jacob Lifshay]

On Tue, Jul 26, 2022 at 8:02 PM lkcl <luke.leighton at gmail.com> wrote:
>
> briefly (v. late here) GPUs went "SIMT"

You're referring to the hardware side, the software side is somewhat
different and is useful without SIMT hardware.

> which is so badly misunderstood as to what it is, it's unreal. SIMT is nothing more than taking a standard processor, replicating it, ripping out every single fetch-and-issue but one, and BROADCASTING the instruction to all others. in all other respects other than fetch/issue the cores are absolutely 100% standard cores including having full independent regfiles (the only standard reg missing of course is a PC, that's all).

Modern GPUs do a bit more than just that, they also have scalar
instructions since why should you waste power for each lane to compute
the exact same value -- just compute it on a separate scalar unit and
broadcast later when you need it.

Jacob