Thursday, January 18, 2007

Is hyper-threading hot stuff?

My home machine recently exceeded the processor temperature threshold when one of my sons was thrashing the CPU with a game. I tried various things like hoovering out the dust and increasing the fan speed, to no avail.

But disabling hyper-threading in the BIOS did the trick, with no perceptable decrease in performance. I was expecting Windows startup to be slower, but I guess it's mainly gated by disk access.

An old ZDNet article claimed that hyper-threading "increases power consumption and thus heat dissipation" which fits my experience.

I could try forcing the game to use a single logical processor, but why bother as I don't seem to need hyper-threading anyway?


AlBlue said...

Most games are unlikely to be seriously multi-threaded though, which means that the HT isn't likely to help out much. However, they are likely to be kept busy all the time (more so than in generic computing tasks where there's not a lot happening) which would explain the heat too.

HT is a really neat idea for utilising the pipeline bubbles that would otherwise be unused; so if you've got multiple apps running (again, which you don't tend to have in a game) then it is beneficial in those scenarios. For example, if you're running an Eclipse IDE in one instance and a runtime PDE/OSGi in another, I'd expect HT would help out a lot there.

Have a look at: if you're interested in how/what HT does.


Glyn said...

Thanks for the article. I don't run multiple apps much at home - I tend to sit in a web browser most of the time.

Further to the blog, my son noticed that Windows media player doesn't play certain kinds of tracks when hyper-threading is disabled! Rebooting, toggling the BIOS setting, and making no other changes (that we are aware of) makes it work properly again. So it seems some applications depend on hyper-threading for correct operation, which I find surprising.

Furthermore, some family members are now complaining that internet access is slow (my other son's machine apparently has normal internet speed), so I guess hyper-threading may run the browser 's multiple threads significantly moe efficiently. Must try some experiments...

Glyn said...

Back with HT enabled and the internet is screaming along. So it seems HT really is hot stuff, in both senses ;-)


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