Please help, GPU overclocking with lowered core voltage?Reliability?

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Gamer-Potatoes

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I have a HD7990 which during it's later days now is no longer keeping up with new titles like Witcher 3.

I have been trying different things to try and improve framerate and reducing microstuttering.

The card has been at stock speeds( 1000MHz/1500MHz, core/mem ) and with reduced voltage for a while now. Voltage was reduced from 1200mV to 1125mV, this did significantly lower temps and actually give a slight performance boost. The two cores used to continuously go between 950MHz and 1GHz, lowered voltage fixed that. Peak temp before used to be as high as 92 Celsius.

Now I have also overclocked it to 1025/1525, as small step up but the voltage is still at 1125.
I have run Heaven for quite a while and I'm seeing consistent results.

Voltages and clock speed are rock steady and I found no observable artifacts in Heaven.

What I'm concerned about is will this be sustainable? I am after all doing a slight OC with reduced voltage. I have also set the power limit to +20%, after increasing the power slider it has become much more stable. Before usage would spike up and down and clocks would also fluctuate by ca 10MHz, now they are rock steady as well.

I have read that the power slider increases the amount of power the GPU can take, but how does that work with my lowered voltage? Will this increase amperage somehow, wattage? Temps are lower and it's more stable but where does the extra juice come from when the voltage is lowered from stock?

I look forward to hearing any ideas any of you might have, and I thank you in advance.
 
Solution
Mr Kagouris


That's a problem right there. As for the power slider, no. The power slider is there for cases where you up the voltage so much the GPU is hitting its actual power limit.

And as for changing the TIM, don't worry about it. It's pretty much the same as changing the CPU TIM, except there's more screws involved (which is why I recommend having a tray to put them in, unlike the first time I did this and ended up sweeping the floor with a magnet), and you usually have to put more TIM on than you would on a CPU. There's nothing that can really go wrong as long as you apply the TIM properly (also have to apply some to the memory chips and VRMs usually, generally just apply it where the manufacturer did) and...
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Mr Kagouris

Mr Kagouris

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Power limit becomes an issue when you raise the voltage too much. Generally it doesn't matter as long as you don't lower it or go beyond AMD's limit to how much you can increase it. As for overclocking, just follow the standard procedure. Raise clock, if it becomes unstable, raise voltage. Rinse and repeat until you get a high stable clock at a reasonable voltage. At this point I'm guessing the GPU is out of warranty anyway, so you could also replace its thermal paste with something a bit more high quality to get better temps (an old card that runs that hot is bound to have degraded TIM anyway so this would be a good idea regardless). Other than this, for better thermals you could consider watercooling it, but for this particular card I wouldn't trust anything less than a full cover waterblock, which would mean custom watercooling, at which cost point you'd be able to get a better card.
 
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Gamer-Potatoes

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Thank you for the reply. However my question is not so much about overclocking in general but overclocking and undervolting at the same time. Temps are no longer an issue, with the reduced voltage peak temps have gone from 92C all the way to 81C with an average of 76, fan speed never exceeds 49%. My concern is more about how increasing the power slider will affect reliability considering the voltage has been lowered by 75mV from stock despite the small OC.

P.S
I don't really have the guts to change the TIM, never touched a screw on a GPU and I can't afford a new GPU if something goes south. Hard times recently.
 
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Mr Kagouris

Mr Kagouris

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Sep 7, 2015
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That's a problem right there. As for the power slider, no. The power slider is there for cases where you up the voltage so much the GPU is hitting its actual power limit.

And as for changing the TIM, don't worry about it. It's pretty much the same as changing the CPU TIM, except there's more screws involved (which is why I recommend having a tray to put them in, unlike the first time I did this and ended up sweeping the floor with a magnet), and you usually have to put more TIM on than you would on a CPU. There's nothing that can really go wrong as long as you apply the TIM properly (also have to apply some to the memory chips and VRMs usually, generally just apply it where the manufacturer did) and don't lose any screws or washers. Especially in cases such as this it would improve your thermals a lot more than you'd think. And while you're worried about screwing something up, consider that lower temperatures increase component longevity.
 
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Gamer-Potatoes

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Don't get me wrong about the fan speed, before undervolting it would spin faster but I'm using the original fan profile, so the fans spin as fast now at 75C as they did before at 75C, it's just that now it doesn't really cross that threshold.

As for the power slider I did find things to be a bit odd. My OC is only 25MHz on the core and memory but when I had 0% powerslider it would throttle, same as 8%, when moved to 12% throttling would occur but after a much longer time, at 20% it has never throttled. Temps are identical though regardless of the powerslider.However if I put the clocks back to stock and voltage with the powerslider on 0% it doesn't throttle until the high 80s, and then it's only by 50MHz.
I really have no idea why it's like that. Any ideas?

Again thank you for the swift reply.
 
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