Low GPU fan speed leads to lower framerates and lower temps?

[pybrick]

I would think that dropping the manual fan speed on a graphics card would always result in higher temps and a resulting lower framerate, but the following suggests that the card lowers GPU usage if the fan speed is much slower (to prevent overheating?) resulting in lower framerates that in turn prevent any chance of overheating.

Graphics: XFX Radeon HD 6870 2GB
Display setup: 3x1 Eyefinity (3430x1920)
Game: Crysis 2

- Fan speed: auto; FPS: 30-40; Load temps: 70-75C
- Fan speed: 20% via Vision Engine Control Center; FPS: 30-35; Load temps: 70-85C
- Fan speed: 0% via ATI Tray Tools (actual speed appears to be 10%); FPS: 15-20; Load temps: 60-70C

Does anyone know why my card isn't overheating at the minimum fan speed I can set?

 

[Gman450]

The decrease in performance can be said as an answer.
The decrease in FPS means that the card is not running 99-100%. It might only be using around 50-60% or so, due to low fan speeds and thereby resulting in low FPS.

BTW, why are you trying to overheat your GPU?

 

[fb39ca4]

It is because the GPU is automatically underclocking or disabling parts of itself or so it doesn't turn into a puddle of melted silicon.

 

[pybrick]

BTW, why are you trying to overheat your GPU?

I wasn't trying to; I had manageable temps with 40% and 20% fan speeds so I wanted see where the temps would be at 10% speed. It's nice to know that they put in that safeguard. It was all in an effort to reduce system noise. Idle temps are higher, but my PC is much quieter. I'll have auto fan control for games where noise isn't an issue and 40% when noise is an issue.

 

[Gman450]

Yeah, put it on auto. Your HD 6870 is just going 70-75C which is actually quite normal. Don't ever let it reach 85-90C etc. That's when you'll need to manually increase the fan speeds to 80/90/100%.