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Old 2016-02-05, 23:16   #3
Serpentine Vermin Jar
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Jul 2014

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Originally Posted by CRGreathouse View Post
I'm interested in comparing CPUs in terms of (among other things!) power consumption. How reasonable is it to assume that power consumption at full load is equal to TDP?
If your cooling is up to the task, you will get pretty close to TDP specs. Close enough that, from an engineering standpoint, you might just say it's the same.

In practice, if you're pushing the thermal limits, your CPU probably won't run at the fastest turbo speed (c0 or whatever) so it'll clock down just enough to keep within the "thermal" part of TDP, which might mean it's power usage is less than the max.

I've mentioned before that on my dual-socket HP Proliants, when stress testing I'll see CPU #1 run at full speed (full turbo state), but CPU #2 is one tick slower, because it's running a bit hotter. I think it has to do with air flow through the system, like air being drawn over the 15K RPM disks up front, design of the air baffle, the proximity of CPU #2 to the array controller (which runs really hot), etc.

Still, you'd be within spittin' distance of max power, like within a couple watts.
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