Question Undervolting

Tahmeed797

Honorable
Oct 28, 2016
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so i recently got myself a 6700xt nitro+ i was gonna undervolt it but then i realized wattman power limit slider is only till 30%, shouldn't it be 50? plus at 30 i cant push down the voltage lower than 1125, even a little lower and display crashes. if anyone can help or guide me it would be appreciated.
 

Tahmeed797

Honorable
Oct 28, 2016
50
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10,530
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Have you used the card without changing the settings? Is there a need to undervolt? Does it run hot and thus cause fans to run all the time? Undervolting is to reduce the heat and noise from the cooling fans and keep the same performance.
Why, specifically?
to answer both of your question, yes i tried the card withtout changing settings, hot spot was 107 degrees and 88 degrees in apex at around 165fps.
 
to answer both of your question, yes i tried the card withtout changing settings, hot spot was 107 degrees and 88 degrees in apex at around 165fps.
You can try undervolting and it is helpful not only to lower temps but also to improve performance. Modern GPU's are very temperature sensitive and anything you can do to keep hot spot temps below 90-95C only serves to improve performance.

Arranging fans to blow cool air into the intake area of your GPU's coolers, or even removing a case side cover, can help a lot with temperature. This may be the reason you're seeing high temps (107C) and instability, especially if you have a glass-side case with a vertical mount GPU.

I'm not sure what voltages are attainable for a 6700XT, but my 6800XT likes to have a setting of around 1068-1081mV for gaming. It can handle one or two passes of TimeSpy benchmark as low as 1050mV at a fairly heavy overclock but it will start throwing a lot of math errors in GPU Folding@Home unless kept above 1081mV even at stock clocks.

But be a bit cautious when increasing the power limiter. While it will most likely handle being pushed up to the max allowed, if you do the GPU will hit hot-spot temperatures of around 90C sooner and then start pulling back on clocks. Test it with back-to-back TimeSpy runs to see when it's hurting and not helping. Maxing the power limiter is usually beneficial only if you have extremely good cooling for the GPU...something like liquid cooling...but people do it a lot and think they've done a trick since it might give a terrific score with one pass at TimeSpy.

Also, AMD has imposed a hard power limit on Navi2 GPU's in the BIOS which mean they they can not exceed certain settings. So if the board partner has already increased the power limit with their (sanctioned) OC model then you only get the remainder to the AMD imposed hard limit. That may explain what you're seeing. There are ways around this with RedBiosEditor (RBE) if you're really interested, but it's definitely hardcore.

And lastly, undervolting may seem a bit strange if you're also monitoring the GPU voltage when in-game where it might hit voltages well above what you set it at. The way it's been explained to me is it's more of an off-set adjustment for introducing a bias to the boost algorithm to make it not hit as high of a voltage in each P-state as it would have before. So it will still hit higher voltages but not likely to hit the max, 1150mV in my case with stock settings
 
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tennis2

Judicious
i realized wattman power limit slider is only till 30%, shouldn't it be 50? plus at 30 i cant push down the voltage lower than 1125, even a little lower and display crashes. if anyone can help or guide me it would be appreciated.
Power limit adjustments and voltage offsets are different things.
  • 6700XT (stock) TDP is 230W (could be slightly higher for the Nitro+). At 100% (+0%) power limit, the card will boost clock speeds until that power draw is reached (assuming voltage, temp, and current limits aren't limiting first, which they typically dont). If you set +30% power limit, the card will now boost until it's at 300W power draw. Vice versa in the other direction (ie -20% power limit)
  • Undervolting (voltage offsets/changes) is the process of defining a new [lower than stock] operating voltage for a given frequency(ies). Take one frequency as an example. If 2000MHz = 1000mV at stock, now maybe you set 2000MHz = 900mV. The vBIOS has a lookup table of the full frequency band and associated voltages to respective frequencies. By setting a lower voltage, the card consumes less power at a given frequency. Because of this, the boost algorithm can now push frequency higher until it hits the set power limit.
    • Voltage offset is simply applying the same reduction (say -100mV) to every frequency point in the lookup table. It's simpler than setting custom voltages for every point, albeit possibly less efficient to reach the OPTIMAL voltage for each frequency.
      • Back when I had an RX480, it was relatively easy, because there were only 7(ish?) points on the WattMan (yes, I still call it that) advanced frequency/voltage table.
      • Conversely, MSI Afterburner for my current 3060Ti has something like 100 points on a graph I have to move around, which is insanely annoying, so I just do an offset to move every point on the graph the same amount.
    • Sometimes voltage offset is flip-flopped and displayed as a frequency offset (+150MHz). Same result. 1000mV=2150MHz
    • Most people confuse undervolting with underclocking.
 
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Teknoman2

Commendable
Oct 13, 2020
101
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First off, you only move the power slider if you plan to overclock. Then, how much you can lower the voltage depends on your card, every single one is different with the tolerances. If you won the silicon lottery you get better results, if not, you are stuck to near stock settings. In your case i guess its the later. To lower temperatures you should look into the fan settings. On my card for example, the auto setting for the fan is to not go over 70% RPM. My card barely ever goes over 65C so i don't need to worry about it but in your case, if there is a limit on the fan speed, you can get the card to cool down by removing it.
 

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