[libre-riscv-dev] Scoreboards

[Samuel Falvo II]

On Tue, May 14, 2019 at 10:49 PM Luke Kenneth Casson Leighton <lkcl at lkcl.net>
wrote:

>  okaay, so then, yes, you'd have absolutely no need of a scoreboard.
>

So, to clarify my understanding, a set of global read reservation and write
reservation masks are alone insufficient to count as a scoreboard?

"silly-tricks-that-have-to-be-done" on a single-issue design, it will
> become clear.
>

Perhaps my questions are asking the wrong question.  I'll just need to play
with the ideas until my Montessori[1]-mind finally figures it out.

  so that's "two stupid tricks" - note in particular that you had to
> *have* the WAW and WAR detection, this is very very important to keep
> in mind in order to answer your question.
>

Sure, I'm not arguing against having the infrastructure.  I'm just saying I
don't see the use-case for, e.g., Q-matrices or the bit-vector linked list
of FUs.  That I don't see the use-case doesn't mean the use-case doesn't
exist!  :)  I was just wondering what sequence of instructions, for
example, would necessitate their existence.

In my thought experiments, I derived my sequencing logic exclusively from
global read and write reservation vectors and individual FU busy flags.  I
don't *think* I had a need for anything more sophisticated than that.

nice.  btw you do know that the 6502 is a super-scalar out-of-order
> design, right? :)
>

I don't see how it's superscalar or out-of-order; can you elaborate on
this?  I'd like to know more.

________
1.  I frequently lament that I'd've been more successful in life had I gone
to a Montessori qualified school instead of the run-of-the-mill public
school.  My brain just seems to be wired in a fundamentally different way
than most people I run across, and it has severely hindered me throughout
life.  But, I'm digressing again.



-- 
Samuel A. Falvo II