[Beowulf] Opinions of Hyper-threading?

Bill Broadley bill at cse.ucdavis.edu
Mon Feb 25 12:12:18 PST 2008

I believe it's actually simultaneous, instructions from 2 different processes 
can run in the same cycle against 2 different register files.

Other chips have vertical multithreading where only 1 process runs in any 
given cycle.

Peter St. John wrote:
> Just for a clarification (for those of us who are hardware deficient),
> hyperthreading (the Intel mechanism) isn't actually simultaneous, correct? I
> had assumed so but I appear to be confused about it. Hyperthreading keeps a
> thread ready to take advantage of stalls in a preceeding thread, but doesn't
> ever actually perform a second instruction in one click tick, correct? One
> might think that there are so many pathways on a modern chip that collisions
> could be managed among several simultaneous threads.
> Thanks,
> Peter
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