Maxwel SLI voltage bug and throttling

[Dirk Diggler]

The following situation happened with my 970 SLI setup. Now I've changed to 980 SLI it's still happening, so it's either my set up or a Maxwell thing.

Firstly the voltage bug. Both 980s will run with one having a lower voltage than the other. However, if I overclock the card with the higher voltage by 30mhz more than the other, they both get the exact same volts.

Secondly, and the one that's bothering me...

GPU1 is at stock.
GPU2 is 30mhz higher clocked than GPU1
In Heaven, both run at 1.212v and core clock is 1392

All is good.

Now, if I slide the voltage up on both cards by the max allowed in AB (87mv) things don't go so well...

GPU1 sits at 1.256v and core clock is 1418
GPU2 sits at 1.262v and core clock is also 1418.

Then the cards start to throttle.

GPU1 throttles to 1.231v and core clock is 1405
GPU2 throttles to 1.237v and core clock is also 1405.

GPU-Z shows perfcap reason as Vrel/SLI.

PSU is Corsair HX850 Plus Gold, and rig draws 550w from the wall under full load. Maximum temperature throughout was 65c.

So, why voltage reliability problems and throttling? PSU?

 

[Gregster]

That is pretty much how GPU boost works and has done that since the 6xx series. If you use AB or PrecisionX, you can force lock voltages and so long as the temp doesn't get high, you should have no problem keeping the clocks high.

 

[Dirk Diggler]

So why does it down clock like that when temps are fine?

Cheers BTW.

 

[Gregster]

So why does it down clock like that when temps are fine?

Cheers BTW.

No idea in truth. It has always been something that annoyed the crap out of me as well. I am on Titans with a custom bios that doesn't use the boost feature, so what I set the clocks at is what they stay at

Not kept up with Maxwell and if there is a bios for the cards, sorry bud.

 

[RanxZy]

These cards are optimised for saving power as well, I wouldn't be too worried as long as gaming performance is acceptable.

 

[Dirk Diggler]

Forcing constant voltage via AB doesn't fix it.

 

[tommybhoy]

https://forums.geforce.com/default/...y-lower-voltage-than-the-other-driver-bug-/1/

If that's similar to what your getting, you might find some info in there.

 

[Dirk Diggler]

Thanks for the link Tommy. It doesn't really provide any solutions, unfortunately.

I've got a sort of work around. With core set at 100 on one and 120 on the other, both cards boost to 1480 and stay there. Voltage is the exact same on each card too.

I've got a +200 memory clock set too, and I'm happy with those settings for 24/7 use.