Question High fan RPM lowers fps - GTX 970

[Tor Jakobsen]

I discovered something I couldn't quite understand yesterday.
I were overclocking my 970, ended up with:
VC: +12
Mem: +500
Core: +160
Power TDP: 120%

However to maintain a proper tempature of no higher than 70C, I put the fan to run at ~75% around that tempature and ~90% at 71-72C.

What I discovered was that as soon as the fan RPM would rise to around max, I lost up to 5 FPS in Furmark benchmark, and lost quite a bit of score.
Even running consistently at 75%/70C lowered the FPS compared to running 50% RPM or less.

I unset the manual fan control in Afterburner, and had it run full auto, now I ran higher fps in Furmark, but my card would reach 78C.

My score in Furmark was also ~4250 with auto fan control and ~4150 with manual.

What could be the reason of this?
Is it because my 550 watt power supply is not powerful enough?
Or is it the 970's circuit that fails to deliver required power to the chip when the fans run high RPM?

Keep in mind the tempature, being 78 or 70 had no affect on the FPS as far as i could see.

 

[The Paladin]

1. PSU you need 500 of quality to run that card at max, and in my experience, it can draw up to 180-230W easy all by itself while gaming, I suggest 650W or 750W
2. have you considered to clean and reapply thermal paste on the GPU processor?

 

[Tor Jakobsen]

Yeah, the PSU might be the answer, not really sure tho.

I won't clean my card or put on new paste as I am going to get a new card soon anyways.

The tempature was not really the main topic here, 78C is fine with me, it performs just fine at that tempature.
But the observation, that high fan RPM directly lowers FPS is what I find interesting.

I have just never heard or seen this before

 

[j121]

do you really need to overclock that card? it should still give you good performance

 

[Tor Jakobsen]

Yes, with a ~17% fps boost in Furmark, it is definitely a good idea to overclock. The 970 is a really great card for overclocking