Undervolting GTX 980 decreases performance?

[RejZoR]

I'm wondering one thing, if someone can explain it to me since I don't quite seem to understand Maxwell 2 GPU entirely yet...

I'm runing my card with modded BIOS at 1405 MHz on core using stock voltage. All nice, great performance in Killing Floor 2 at 1080p Ultra settings. But the fans are a bit noisy so I've decided to undervolt it a bit. From stock BIOS setting of 1.281 V which is the maximum allowed, I've tuned it down to 1.2V. With no change in fan noise because supposedly Strix cards are locked to 1.2V anyway. Bumped the voltage even lower to 1.181 V. Fans are significantly quieter now, but I think I'm sensing framerate isn't as fluid as it used to be at 1.2V for whatever reason. Clocks are still running at solid 1405 MHz which is why I'm confused. If clocks were dropping, I'd understand, but they don't.

Question here is, is there some logic in the Maxwell 2 that causes this or is it simply because the GPU is on the edge of being stable, but not able to perform good? I've never experienced something like this...

 

[Dethroy]

[...] but I think I'm sensing framerate isn't as fluid as it used to be at 1.2V for whatever reason. Clocks are still running at solid 1405 MHz which is why I'm confused. If clocks were dropping, I'd understand, but they don't.

sensing = guessing/eyeballing or actual legit fps comparisons?

 

[RejZoR]

Just visually for now. I notice things like this really fast because they super annoy me. Which is why I'm even asking this.

 

[Dethroy]

Just visually for now. I notice things like this really fast because they super annoy me. Which is why I'm even asking this.

Might simply be a case of your mind playing tricks on you. I'd verify your feeling with factual proof.

 

[okidna]

Have you tried checking your GPU PerfCap?

 

[RejZoR]

Might simply be a case of your mind playing tricks on you. I'd verify your feeling with factual proof.

How? I can't bench in KF2 because framerate is different on different game segments. Not aware of timedemo functionality.

@okidna
I think it's not affected, but I was focusing on clocks a bit more. Will recheck that, but I think it wasn't getting triggered.

 

[Dethroy]

How? I can't bench in KF2 because framerate is different on different game segments. Not aware of timedemo functionality.

If your undervolting would have any impact on your GPU's behaviour you would notice them in benchmarks as well, not just in Killing Floor 2.

 

[RejZoR]

It seems setting same low and high voltage for a specific clock step helps stability and this weird behavior. Instead of giving GPU a range, setting both low and high the same seems to help stability a lot. Yesterday managed to limit the GPU to 200W TDP at 1405 MHz core at only 1.150V (at the 63 clock/voltage step. Passed 3DMark Extreme stability test and a round of Killing Floor 2 without any triggered utilization protective features. Need some more testing but so far it's looking good. I know it's very specific card tailored, but there seems to be quite some hidden efficiency in these old clunkers.