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Does it make sense to "undervolt" a GPU to get cooler temperatures?

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hsjj3

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Discussion starter · #1 ·
A few days back, I came to a realization that Nvidia GPUs have a voltage value attached to a particular clock.

In my case, at stock settings, I got 1206mV = 1418MHz, 1187mV = 1405MHz, 1168mV = 1392MHz etc. Due to thermal/power throttling, I would go as low as 1106mV = 1054MHz. It's about 6 or 7 levels below the max.

Then, I got round to overclocking. First by +80MHz, then by +110MHz. And I was shocked. In the case of the latter, now 1206mV = 1527MHz, 1187mV = 1515MHz...1106mv = 1455MHz, 1093mV = 1443MHz.

So, as you can see, By +110MHz OC, at 1106mV I am seeing +100MHz clockspeeds.

To my understanding, voltage is the biggest cause of heat production of a GPU.

So I was wondering, is it somehow possible to make 1168mV as my new max voltage? Do you think it'd be a sensible thing to do? I think it should be able to cool down my GPU much better if I undervolted it by two or three increments. Apparently I have a "good" quality GPU which allows me to +110MHz (I tested up to 132Mhz, very stable, no artifacing) and +193MHz to memory despite the fact I didn't raise the power limits or overvolt and the fact my GPU is a single-fan iTX model.

Would love to know how to do this.

Thanks!
 
#2 ·
People including me have undervolted CPUS before. It would be the same concept. See how low it goes and is stable stock with lower voltage and of course it will run cooler. OEM spec is setup so every card runs 100% at that clock. It's the silicon lottery for a reason so i would see a few mvs dropped off and lower temps
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#3 ·
If your not a heavy overclocker, you can edit the bios of you gpu to run at a lower voltage while still having a mild overclock.

My 7950s default voltage is 1.25v and default clock of 900mhz. I was able to get the voltage down to 1.13v and still have the core clocked at 1100mhz. As you can imagine the reduction in voltage was a substantial reduction of temps and fan noise.

If your card has a dual bios you can edit the bios and just slowly lower the voltage till its not stable in benchmarks at the clock speed you desire.
 
Discussion starter · #4 ·
Quote:
Originally Posted by Socks keep you warm View Post

People including me have undervolted CPUS before. It would be the same concept. See how low it goes and is stable stock with lower voltage and of course it will run cooler. OEM spec is setup so every card runs 100% at that clock. It's the silicon lottery for a reason so i would see a few mvs dropped off and lower temps
thumb.gif
Click to expand...
Yeah apparently I got a good lottery. My thinking is, since I can hit 1443MHz at 1106mV (100mV less) after a 110MHz overclock, which is HIGHER than the 1418MHz I hit at stock settings at 1206mV (100mV more)...with undervolting by nearly 10% I can still hit a much better clock speed. Don't know if it makes sense though.
 
#7 ·
Quote:
Originally Posted by hsjj3 View Post

How did you do it? MSI AB doesn't let me undervolt even after unlocking voltage control.
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Oh, just the overclock + power limit trick. +115 on the core and 80% power limit. I'm sure a bios mod allows using locked voltage values. Some folks here I think can even modify the bios for you.
 
Discussion starter · #8 ·
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Originally Posted by Smanci View Post

Oh, just the overclock + power limit trick. +115 on the core and 80% power limit. I'm sure a bios mod allows using locked voltage values. Some folks here I think can even modify the bios for you.
Click to expand...
The power trick doesn't work for me. However, lowering the temperature limit works, but it still results in variable clock speeds as the card approaches the temp limit. I was hoping with a voltage limit instead, it will result in lower initial boost, but eventually smoother boost values. Currently the boost starts off higher and goes lower quickly, unnecessarily heating my card up for the first 30 seconds or so.
 
#9 ·
Undervolting prevents throttling and is overall great for the chip, as long as you keep it stable.
 
#10 ·
Quote:
Originally Posted by hsjj3 View Post

The power trick doesn't work for me. However, lowering the temperature limit works, but it still results in variable clock speeds as the card approaches the temp limit. I was hoping with a voltage limit instead, it will result in lower initial boost, but eventually smoother boost values. Currently the boost starts off higher and goes lower quickly, unnecessarily heating my card up for the first 30 seconds or so.
Click to expand...
Wow, I just downloaded a 980 bios and Kepler bios tweaker, man Nvidia bios editing is way more complicated then ATI.....
 
#14 ·
Ideally, processor power consumption goes up with the square of the voltage and linearly vs frequency. Looking at your values
  • 1206mV @1418MHz
  • 1187mV @ 1405MHz
  • 1168mV @ 1392MHz
and
  • 1206mV @ 1527MHz
  • 1187mV @ 1515MHz
  • 1106mv @ 1455MHz
  • 1093mV @ 1443MHz
we can find the ratio between the lowest overclock and the highest stock speed:

(1093mV/1206mV)2*(1443MHz/1418MHz)*(100%) = 83.6%

In other words, you've cut power use - and therefore heat production as well - by a sixth and gained (negligible) performance. But semiconductors also have an interesting quirk compared to, say, metals. When heated, their impedance decreases and causes them to draw more power (which heats them further, causing them to draw more power and heat...). That's one reason why AMD's Fury X can draw as little power as it does, and I think it's actually more efficient than the 980Ti or Titan X by a small amount. The temperature has a hard limit of 65°C, much cooler than about any other GPU on the market, which reduces wasted power.

Undervolting is a tried and true tactic for lowering a system's power. Stock voltages, I believe, are there so every single piece of silicon shipped out is guaranteed to hit those frequency targets. Even if you get an average processor, undervolting it is feasible to some degree. AMD's CPUs are really bad about it. FX 8 cores can hit like 1.1-1.2V with a bit of effort, down from the stock 1.3-1.4V, which with no other changes cuts power by 15% minimum.
 
#16 ·
Quote:
Originally Posted by hsjj3 View Post

Ok, but now given that it is clear undervolting will reduce temps/power, I would like to know, how do I go about doing it?
Click to expand...
Well you would need to alter the Vbios.
For a CPU it is much more simple lol.
 
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Socks keep you warm
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