Re: OoO execution (was: The Seymour Cray Era of Supercomputers)

On Mon, 19 May 2025 17:46:45 GMT, anton@mips.complang.tuwien.ac.at
(Anton Ertl) wrote:

John Levine <johnl@taugh.com> writes:

The 360/91 had primitive branch prediction in "loop mode".  It had an
eight doublewprd instruction queue (which it confusingly called a stack.)
If a program did a backward branch of less than eight doublewords, it'd
stop prefetching and execute out of the queue until the program fell or
branched out.

>
The 68010 had a similar feature (with a smaller buffer), but I don't
think one would call it branch prediction.  In any case, I meant
speculative execution based on branch prediction (but did not write it
that way), and the 360/91 did not do speculative execution AFAIK.
>
- anton

Most DSPs have some kind of "loop buffer" from which they can execute
without fetching code from memory.