How does voltage limit/power limit work?

[Mayh3M]

Noticed one of my 980 Tis is always voltage limited according to MSI Afterburner (it's at one instead of zero), even at stock.

It's boosting to 1300+ and overclocks to 1500+ so I'm curious about how voltage works.

I thought voltage scales with clock speed? Seems more complicated than that.

I tried increasing voltage by +87 while leaving everything at stock, and the card now boosts to 1340+, including in SLI mode.

 

[andybird123]

There is a boost table in the BIOS that steps up by boost and at each step has a min and Max voltage, however what determines the actual voltage is unclear. Presumably the BIOS has some sort of lookup or detection for what voltage it thinks the GPU needs, but in this case it's trying to go too far and push the voltage too high, hence hitting the limiter.

When you add to the base clock, I'm not sure if it pushes you up or down the boost table, if it is down then it could mean the card then stops trying to push too much voltage, or if up then its raising the voltage limit slightly allowing the higher clocks before hitting the limit.

 

[Mayh3M]

There is a boost table in the BIOS that steps up by boost and at each step has a min and Max voltage, however what determines the actual voltage is unclear. Presumably the BIOS has some sort of lookup or detection for what voltage it thinks the GPU needs, but in this case it's trying to go too far and push the voltage too high, hence hitting the limiter.

When you add to the base clock, I'm not sure if it pushes you up or down the boost table, if it is down then it could mean the card then stops trying to push too much voltage, or if up then its raising the voltage limit slightly allowing the higher clocks before hitting the limit.

Interesting. I thought this was the case. But its odd that the card at stock is hitting a voltage limit. This is the EVGA 980 Ti SC ACX.

Is it a problem at all hitting the voltage limit in this manner, as in the card being completely at stock?

 

[andybird123]

No, it just means the stock setting is stopping the card from boosting any higher, but that is what afterburner/precisionx is for, to overide the stock settings and give you a bit of manual control of how it overclocks

 

[Mayh3M]

No, it just means the stock setting is stopping the card from boosting any higher, but that is what afterburner/precisionx is for, to overide the stock settings and give you a bit of manual control of how it overclocks

Right. So voltage seems to be somewhat independent of clock speed and is instead based on its own 'boost table' or clock cycle as you said.

Thanks for clarifying.