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If I have a laptop with an i7 that I decide to throttle the maximum processor state to 50% on battery power, what happens in regard to HyperThreading?

Does it get activated at 50% frequency? or does it just not really even touch the four extra threads?

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I don't think you mean hyper-threading. Turbo boost, perhaps? – Eroen Feb 29 '12 at 17:49
@Eroen No, Azolo means Hyperthreading, i7 has… – Moab Feb 29 '12 at 20:53
I made the assumption because the rest of the question would fit better to TB. The concepts of frequency scaling and dynamic activation are rarely confused into HT. =) – Eroen Mar 1 '12 at 10:15
@Eroen In a way you were right, but I was unzipping Mingw-w64 yesterday and it was painstaking watching how slow it was at 50% frequency. Ends up nothing was happening fast enough for the cpus to care about HT (which is where TB comes in). I did manage to get HT doing something at 50% frequency after reading mastashake57'sanswer. – Azolo Mar 1 '12 at 16:59
up vote 2 down vote accepted

My understanding is that HT is an either ON or OFF mechanism that can be controlled by your system BIOS. Regardless of whatever throttling mechanism you have enabled to clock down your CPU, HT will be enabled if you have it set that way.

This article explains the power consumption levels on an HT enabled CPU. If your concern is power saving features over performance, you could see more battery life if you turned oFf HT.

Hope this helps!

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You're totally right, but it took me a lot of work for it to touch the "parked" cpu. I guess stuff just doesn't get done fast enough for timing to matter at 50%. Killer link though =) – Azolo Mar 1 '12 at 1:32

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