Re: Stealing a Great Idea from the 6600

On Sun, 21 Apr 2024 18:57:27 +0000, mitchalsup@aol.com (MitchAlsup1)
wrote:

BGB wrote:

Like, in-order superscalar isn't going to do crap if nearly every
instruction depends on every preceding instruction. Even pipelining
can't help much with this.

Pipelining CREATED this (back to back dependencies). No amount of
pipelining can eradicate RAW data dependencies.

This is quite true. However, in case an unsophisticated individual
might read this thread, I think that I shall clarify.

Without pipelining, it is not a problem if each instruction depends on
the one immediately previous, and so people got used to writing
programs that way, as it was simple to write the code to do one thing
before starting to write the code to begin doing another thing.

This remained true when the simplest original form of pipelining was
brought in - where fetching one instruction from memory was overlapped
with decoding the previous instruction, and executing the instruction
before that.

It's only when what was originally called "superpipelining" came
along, where the execute stages of multiple successive instructions
could be overlapped, that it was necessary to do something about
dependencies in order to take advantage of the speedup that could
provide.

John Savard