Dragonfly and Hyperthreading....

[Matthew Dillon]

:..
:balance the workload across what it believes is two real CPUs, with
:separate caches, separate ALUs, and separate FPUs, which doesn't work
:on an HT CPU).  And those systems that do have an HT-aware scheduler
:don't always do a good job of keeping things running smoothly.  You
:get much more reliable performance when HT is disabled.
:
:Other CPUs that use SMT (like IBM's POWER4 or POWER5) built into the
:design from the get-go (rather than kludged on afterward like with the
:P4) work much better.  Don't have much info on this beyond what's on
:Ars Technica, though.
:
:-- 
:Freddie Cash, CCNT CCLP        Helpdesk / Network Support Tech.

    POWER4 at least is a multi-core design, not an HT design, which is why
    it works a whole lot better :-)

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>