relationship between CPU frequency and TDP

Turbonium

Platinum Member
Mar 15, 2003
2,154
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91
Warning: newb question ahead.

With two otherwise identical CPUs running at different frequencies, the CPU running at a higher frequency will always have a higher TDP (and obviously higher power consumption), correct?

Assuming the above to be correct, how do you explain, among other examples, the following?:

Core i7 920 (2.66 GHz)
vs.
Core i7 950 (3.06 GHz)

In the above example, we see one CPU running a full 400 MHz faster than its counterpart, but at the same TDP (130 W). Assuming this isn't an error or inaccuracy, please explain why this is the case.
 

Piroko

Senior member
Jan 10, 2013
905
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Power consumption and frequency are (fairly) linearly dependent on each other, correct.

Intel and AMD only list steps of TDP - like 45W, 65W, 95W and 130W. Thus, two processors with a difference of 30% in power consumption could be listed in the same TDP bracket.
 

Borealis7

Platinum Member
Oct 19, 2006
2,901
205
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in before IDC! =p
I think the TDP is more relevant for the board makers and cooling makers than us ordinary folk, because the board makers have to know whats the maximum amount of power the cpu will draw from their board and must design the circuitry in accordance, and the cooling makers have to know how much heat they have to dissipate from the CPU when its running full blast.
 

Abwx

Lifer
Apr 2, 2011
11,630
4,501
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TDP is linearly frequency dependent but this is assumed at a fixed voltage
of course , as TDP is square law voltage dependent , so if a given CPU needs
a very slight increase in voltage to sustain a said frequency it will dissipate
way more than a CPU that has lower operational voltage.
 

Idontcare

Elite Member
Oct 10, 1999
21,110
59
91
TDP is linearly frequency dependent but this is assumed at a fixed voltage
of course , as TDP is square law voltage dependent , so if a given CPU needs
a very slight increase in voltage to sustain a said frequency it will dissipate
way more than a CPU that has lower operational voltage.

And assumes fixed temperature as well.

In practice, because the higher clockspeed results in higher power consumption, and the higher power consumption results in higher operating temperatures, the higher operating temperatures feeds back into the static leakage portion of the equation and causes even more power consumption still.

PtotalVccTGHzSymbolicEquation.png




TDP is square law voltage dependent for dynamic power, but is exponentially voltage and temperature dependent for static power losses.