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ThermalDesignPower and its calculation(doubt)

post #1 of 8
Thread Starter 
I have a friend who wants to know how calculate his card`s tdp,he has a hd 6970 and he wants to replace the heatsink due to high temperatures(reference model),do you know any formula for its calculation?or the TDP is the maximum allowed heat transfer from the power input?
post #2 of 8
You don't calculate it (well, maybe the Development Engineers can) you measure it.

http://www.anandtech.com/show/4061/amds-radeon-hd-6970-radeon-hd-6950/24

http://www.bit-tech.net/hardware/graphics/2010/12/15/ati-radeon-hd-6970-review/10

http://www.guru3d.com/articles_pages/radeon_6950_6970_review,11.html
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post #3 of 8
Thread Starter 
but he wants to know the TDP at a certain vcore. A hd 6970 is 250w but is it the maximum? And the question is Thermal output not consumption
post #4 of 8
Quote:
Originally Posted by PontiacGTX View Post

but he wants to know the TDP at a certain vcore. A hd 6970 is 250w but is it the maximum? And the question is Thermal output not consumption


The manufacturer suggested specs are just that suggested. The reality is that Cayman has no nanny imposed limits like Tahiti does in its asic. Thus as you raise voltage power draw rises accordingly. Personally I never got to test nor was it really a concern what power draw was like with a lot more voltage because in my case my loop/psu were overbuilt for that purpose. Even though I never measured it, I know first hand that pushing the overclocks on my old unlocked 6950 quad array fried a few 1200w psus until I moved up to a 1500w unit. To answer your question of whether the 250w limit is absolute or not? Imo, it is not.
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post #5 of 8
i suppose if you wanted to be absolutely conservative and get a quick answer then if you measure the power drawn by the card (or maybe the delta between idle and full GPU load) then since the card can't produce a greater heat load than power drawn (otherwise you'd have a perpetual motion machine) then a heatsink that can handle that power will be fine.

There isn't going to be a generic formula for heat output though. One thing you could maybe do is use the relation that P = V (squared) / R. since R is near enough constant the power will increase by the voltage squared.

If, say, it requires 250W of cooling at 1.2vcore then at 1.3vcore it would require 293W.

However there are many, many more factors that will come into play and really the only way to know would be to measure it.
 
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post #6 of 8
Quote:
Originally Posted by pharcycle View Post

i suppose if you wanted to be absolutely conservative and get a quick answer then if you measure the power drawn by the card (or maybe the delta between idle and full GPU load) then since the card can't produce a greater heat load than power drawn (otherwise you'd have a perpetual motion machine) then a heatsink that can handle that power will be fine.

There isn't going to be a generic formula for heat output though. One thing you could maybe do is use the relation that P = V (squared) / R. since R is near enough constant the power will increase by the voltage squared.

If, say, it requires 250W of cooling at 1.2vcore then at 1.3vcore it would require 293W.

However there are many, many more factors that will come into play and really the only way to know would be to measure it.

That's a decent approximation, but transistors have a nasty habit of being nonlinear biggrin.gif


Have you tried HWInfo64? My 7950 has a bunch of current sensors for the GPU, memory, VRMs and such. If your 6970 does, you can just multiply the current and voltage of various onboard components to get a very accurate power measurement.
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post #8 of 8
Thread Starter 
Quote:
Originally Posted by brucethemoose View Post

That's a decent approximation, but transistors have a nasty habit of being nonlinear biggrin.gif


Have you tried HWInfo64? My 7950 has a bunch of current sensors for the GPU, memory, VRMs and such. If your 6970 does, you can just multiply the current and voltage of various onboard components to get a very accurate power measurement.
i will say him.I dont have his card.
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