Overclocking A GPU

[Zein Elrejal]

Hi all,

I ran into trouble while attempting to overclock my new GTX 670 FTW, l ran the Precision X software and started by raising the clock by 20 MHz, the fan to 80% and power to the MAX 145%. Then l started 3DMark 11 to stress test it. Next thing l heard a scary crackle from the machine and the PC shut down, l checked it and l found out that l lost my PSU (650W TX Corsair)!

What exactly went wrong? What have l done?

 

[slomo4sho]

Whether it was on its last leg or was brand new is irrelevant, you overloaded your PSU. Although a 650W PSU would be more than enough for a single GTX 670, not all PSUs are created equal. You may have had a defective unit or you have had it long enough to where its capacity was reduced enough to cause a failure. Here is hoping it didn't take anything else with it.

 

[Zein Elrejal]

Whether it was on its last leg or was brand new is irrelevant, you overloaded your PSU. Although a 650W PSU would be more than enough for a single GTX 670, not all PSUs are created equal. You may have had a defective unit or you have had it long enough to where its capacity was reduced enough to cause a failure. Here is hoping it didn't take anything else with it.

It was brand new.
But that brings me to my initial question, did l do anything wrong?

 

[fkr]

yes. whenever you overclock never increase the voltage until you have found out how much you can push at stock voltage. Then do the smallest increase in voltage possible and then increase your GHz some more.
next time use unigine heaven benchmark. you can just let that keep running while you change your clocks and voltages in real time while unigine is running.
In your case i think you would have had this problem sooner or later no matter what.

 

[slomo4sho]

It was brand new.
But that brings me to my initial question, did l do anything wrong?

No, 20 MHz increments is perfectly reasonable. You just lucked out and ended up with a bad PSU.

yes. whenever you overclock never increase the voltage until you have found out how much you can push at stock voltage. Then do the smallest increase in voltage possible and then increase your GHz some more.
next time use unigine heaven benchmark. you can just let that keep running while you change your clocks and voltages in real time while unigine is running.
In your case i think you would have had this problem sooner or later no matter what.

Although you are correct, I don't see this being a reason for the PSU frying. Higher voltage would have potentially kills the GPU but the PSU failing just indicates a bad unit.

 

[fkr]

do you think it is okay to just jump the card up to 145% max power right away. I do not think anything would happen 99% of the time but I still do not like to jump right up to higher power without testing incrementally how the card reacts to more power. the small jump in MHz overclock is definitely not the issue but I think it is a risk to jump power up without testing at stock voltages first.

In all fairness to the OP what you did is not that risky and should not have caused any problems. you have a bad PSU and hopefully the safeguards they have put into your PSU have saved your other hardware.

 

[Zein Elrejal]

Thanks fkr & slomo4sho.

My new PSU is 750W Cooler Master GX. Should l attempt OCing again? I am scared now!

Any advice?

 

[fkr]

well you have 60 amps on the 12v rail so you should be good there.
have you bought it yet? if not look into seasonic
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151095
If you overclock again make sure you have unigine running while you change things so that you can see when things start going wrong

 

[manofchalk]

The 145% max power doesnt correlate to voltage, but the amount of power your allowing the card to draw. At 100%, the 670 has a cap on its power draw of 170W at stock, if it goes over that it will throttle itself. By raising this allowance, your letting the card draw more power and therefore not limits its performance.

 

[fkr]

yep
It's quite different from voltage control. It's something more akin to 'wattage control'. Your card has some amount of 'juice' it's expected to run at, at a maximum. Let's say you have 2 x 6 -pin connectors on your card + the power from the motherboard. The max 'rated' wattage draw from each of these three connections is 75W, and you have 3, so the absolute max wattage draw that AMD is going to 'allow' your card to draw is 225W.

However, they likely 'expect' a card with this connector configuration to draw something like 175W. Lets call that wattage amount the card's TDP, for the sake of simplicity.

So, when your power limit is set at 100%, this means your card is 'limited' to it's TDP, and if whatEVER you're doing with the card is causes it to exceed a draw of 175W, the driver will start to downclock and downvolt the card in order to get it run within the expected power envelope designated by the power target slider and the TDP.

Raising the Power Target up simply allows for your card to draw more juice through it's three connectors without resorting to downclocking/volting. In the scenario I described, it's likely that whatever % value you have available over 100% is going to reflect the difference between TDP and 'max safe wattage draw', based on the connectors running to your card. If your card indeed had a TDP value of 175, it's likely that max power target would be 100% + (225-175)/175 * 100, or 128% maximum power target.

So, when you OC, and especially when you OV your card, you are obviously likely to increase the power draw of the card (depending of course on the intensity of the test, whether you have v-sync on, these types of things), and if you don't raise the power limit, it might well cause the card to downclock/downvolt when you don't want it to.

 

[Zein Elrejal]

I was thinking of adding an Arctic Accelero cooler for the GPU, but now l am not sure if the new PSU will handle it, what do you think?

 

[manofchalk]

Dont bother with aftermarket GPU cooling unless your outright water-cooling the thing (talking custom water, not a Accelero Hybrid). Even if you did go for it, the PSU wouldnt be an issue. A fan draws maybe 3W at most.