TDP vs actual heat output

[Memphis Raines]

Just looking for some info on a recent upgrade from a 7970 to a 980Ti..


I have a watercooled system that ran quite happily with the 7970 and a 4770K cpu and a moderate overclock on both..

i swapped the 7970 (with a TDP of 300watts) for a 980ti (with a TDP of 250watts) so by that logic i expected in the same games i would experience similar (or possibly lower) temps...

but it actually is the opposite.. temps would be rock steady around 45 - 50 degrees on the 7970, and now the 980ti pushes temps to 65 - 70 degrees and above and with a louder fan profile on the radiator..

I have checked the loop for seating issues and airlocks etc, so i dont feel its a watercooling fault..

I also understand the cpu may be working a bit harder with than before, but i really expected a lower TDP card to output less heat?

or have i missed something somewhere ?

cheers!

 

[humbug]

TDP can mean pretty much anything, it can be used as an average best case heat output or as a recommended TDP.

Your experience of that is a prime example, that 7970 does indeed have a TDP of 300 Watts, actual power consumption is somewhere between 220 and 240 watts, my old 290 was the same with a TDP of 300 Watts and yet it actually pulled 230 Watts

The 980TI pulls at least 250 Watts, my 970 has a TDP rating of 165 Watts, for as good as i think its actual efficiency is i'm under no illusions that it probably pulls a good deal more than that most of the time.

This is an example of AMD putting down a recommended TDP rating and Nvidia using it as a marketing tool to highlight their cards efficiency.

 

[Memphis Raines]

Yeah, I know that the 980ti runs up to 109% as well, esp in games like witcher but only 90% ish GPU use, but in assassins creed syndicate it was 99% GPU but only 80% ish power..

Very good cards but quite a challenge when trying to plan a cooling setup hah

 

[Gregster]

What TDP means is the amount of heat being generated and needing to be removed to keep the card running optimally. The 290X was pretty poor for this with the reference cooler and would throttle quite a bit if the fans were not running at max (just an example and not a dig).

 

[Jokester]

Temperature isn't a measure of power, it could be lower power but less able to get rid of the heat into the loop. A good indication of an increase or decrease in your GPU power output is whether your CPU temperature has changed at all, but even then it takes a fairly large increase in power to raise the temperature in a loop by 1degC all other things being equal (typically need about 250W from memory).

 

[humbug]

What TDP means is the amount of heat being generated and needing to be removed to keep the card running optimally. The 290X was pretty poor for this with the reference cooler and would throttle quite a bit if the fans were not running at max (just an example and not a dig).

Heat is power consumption converted into heat, that heat in this case is measured in TDP, a GPU using 250 Watts will convert 250 Watts of heat (TDP) no lower, no higher, no matter what make / model the card is or what cooler it has on it, its physics, its a universal constant.

 

[Kaapstad]

Temperature isn't a measure of power, it could be lower power but less able to get rid of the heat into the loop. A good indication of an increase or decrease in your GPU power output is whether your CPU temperature has changed at all, but even then it takes a fairly large increase in power to raise the temperature in a loop by 1degC all other things being equal (typically need about 250W from memory).

+1

Poor design of waterblocks and how well they are fitted can account for a difference in temps even though the TDP is the same for two different cards.

OP how much rad area do you have ?

 

[Kaapstad]

Heat is power consumption converted into heat, that heat in this case is measured in TDP, a GPU using 250 Watts will convert 250 Watts of heat (TDP) no lower, no higher, no matter what make / model the card is or what cooler it has on it, its physics, its a universal constant.

TDP results in Heat, Sound and the Output of the card but basically you are on the right track.

All energy eventually ends up as heat.

 

[humbug]

TDP results in Heat, Sound and the Output of the card but basically you are on the right track.

All energy eventually ends up as heat.

Yeah, the key is in the acronym (Thermal Design Power) if you have a 200 Watt card you could rate it as 200 Watts TDP indicating to your board partners a 200 Watt cooler is necessary.

Or you could rate it at 300 Watts because you want your partners to use better 300 Watt cooling, that doesn't mean the card has 300 watt power consumption, its still the same 200 watt card.

TDP is utterly useless as a measure of power consumption, that's not what its for.

 

[Memphis Raines]

the system is running a single 240mm front mounted rad. Tho that might seem undercooled, it run perfectly fine for over a year in its original config with the 7970.. even when it was quite dusty..

It really does show how much actual heat output can vary between similar rated cards

and yes both gpu and cpu temps are higher than before..

I have even tried adjusting pump speed...

drifting back into a more watercooling area, i am going to be upgrading the cooling anyway ready for a X99 SLI config so rather than re using the rad i will be replacing it with a couple of new bigger ones.. which should solve any cooling problems