GPU vs CPU cooling

[Dopekitten]

I've been curious about this for a while.

So basically I don't understand why CPU and GPU temps are roughly the same for differently sized coolers at different sized coolers at different tdps. I.e., looking at some like a gtx 780 ti with the stock cooler going to maybe a max temp of 80C under full load with a tdp of 250W, but something like an i7 4770k goes to the same temp at full load under a larger cooler like the 212 evo, with a much lower tdp, (under 125W).

What am I missing?

 

[lehtv]

The i7-4770K's integrated heat spreader - the outer shell of the CPU - contacts the CPU itself via low quality thermal interface material. I.e. some cheapo paste that does the job so that the chip doesn't overheat in normal conditions. This is mostly why you see the temperatures on the Intel chip reach quite a bit higher levels than they should given the TDP and the size of the cooler. Replacing the TIM with some high quality paste can improve cooling performance drastically. E.g. see this chart from the Finnish tech site Muropaketti.com.

I'm not sure what kind of TIM NVIDIA and AMD use on the GPUs, or if the IHS is soldered on like it used to be in Intel chips up to the Sandy Bridge architecture. However I'm pretty sure that the 780 Ti in particular doesn't even have an IHS, the cooler contacts the GPU directly.

 

[serpretetsky]

another possible reason:
die size of 780ti ~500mm^2
die size of 4770k ~ 180mm^2

Given identical conditions and cooling aparatuses, for the same given temperature a 780ti has 3 times as much area to pump heat through. This directly translates to dumping 3 times as much heat for any given temperature.

edit: actually, I think that assumes that the cooling aparatus is an ideal device that can absorb all heat without rising significantly in temperature. So Maybe under a really good water cooling unit or phase change you should see the 780ti dumping 3 times as much heat for the same tempearture. For regular coolers it will probably be less.