DragonFly users List (threaded) for 2005-02
Re: Dragonfly and Hyperthreading....
is that performance is extremely assymetric. You could waste hundreds
of man hours writing an HT aware scheduler and still not have it work
well for all situations.
Microsoft implemented in a way that made many people happy, and HT had
it's impact on the minds of many. There should be some reward, but i
don't know what impact such implementation could have on the rest of the
code. Could you give us some details?
Even more to the point, HT technology was most useful in past yearsAFAIR Intel intentionally slowed down pipeline operations to the
execution units, so they could push up the clock frequency, to show
customers some really high numbers, and later (2004) they discovered
netburst isn't going to go to 10Ghz, as they predicted in 2003.
when instruction pipelines were not able to make full use of the cpu's
resources. That has changed as well. Today's cpu's instruction
pipelines are able to utility a far higher percentage of the cpu's
available resources, making HT a lot less useful. HT has only been
I think this is an Intel specific mistake, but nonetheless makes SMT
useless on cpus with well designed pipelines.
viable up till now because Intel's cpu architecture sucks rocks comparedMaybe HT will be the only way to gain more effectiveness with lower
clock frequency on netburst (P4).
with AMD's, but Intel can no longer compete by boosting clock rate so
now they are stuck... they have to slow their cpus down and make them
more efficient, and that will kill HT's effectiveness even if you
ignore the heat issue.
My point of interested is what's AMD making better?