6950 driver stopped responding

[Marvos]

Hi. I'm overclocking my 6950 with MSI afterburner 2.1.0

Original clocks are 800/1250. When I run 3DMark11 with that, it works.
Then I overclock the card to 900/1350 and run 3Dmark again. This time it fails (lost window focus) and as the application closes I see the popup in the notification area saying that the driver stopped responding and has recovered. I'm running CCC 11.5. Card is not overheating.

Funny thing is, it worked with 900/1350 just 2 hours ago.
Worth noting: I was messing with the clocks before this happened, ppl on other forums said their 6950s are running at 950/1450, so I overclocked mine to those clocks too (in steps of 10Hz, no more), testing with GPUTool to catch any artifacts along the way. None appeared, so I left it at 950/1450 and ran 3DMark, thinking I'll get UBER results.

What could be the problem? My PSU not supplying enough power? Is it damaged now? It says it can do max 550W, and I also have an Intel quad Q6600 OC'd to 3.2GHz on this system.

Motherboard :Gigabyte P35-DS3
CPU: Intel Core2 Quad CPU Q6600 @2.4GHz OC'd to 3.2GHz
GPU: AMD Radeon HD6950 shaders unlocked
Memory: 2x Ceon DDRII800 2Gb CLS (FSB: DRAM 5:6)
PSU: POWER Pentium IV & PFC model LC6550G version 2.0
OS: Win7 Ultimate 32bit
HDD1: WDC WD10EADS-00L5B1 ATA
HDD2: ST3500 320AS ATA
Monitor (not sure if it helps...): AOC 2216
Audio device(integrated): High Definition audio device (lame, I know )

anything else you need?

[erocker]

Please list your complete system hardware specifications.

[jayc]

You didn't post what voltages are used for that overclock. <--- crucial information.
Did you leave voltage on 1.1v?
Sounds like you need to bump voltage up

[Marvos]

I hadn't tought of that. Afterburner says applied voltage is 1.1V.
I have no problem fiddling around with the voltage, but I'm afraid I'm gonna fry the card. If clocks can be raised without the risk of frying the card, is that true for the voltage as well?

How do I start with this? Bump the voltage up 50mV at a time and keep it as low as possible while maintaining stability?

[jayc]

Originally Posted by Marvos

I hadn't tought of that. Afterburner says applied voltage is 1.1V.
I have no problem fiddling around with the voltage, but I'm afraid I'm gonna fry the card. If clocks can be raised without the risk of frying the card, is that true for the voltage as well?

How do I start with this? Bump the voltage up 50mV at a time and keep it as low as possible while maintaining stability?

Theres your problem.
At the 900/1350 clock You can jump straight to 1.175V, which is the same voltage as a 6970.
Then test.
Adjust speeds again, retest.
Move voltage up if it crashes or artifacts are seen.
Retest.

Safe voltages would be 1.2v - 1.25v.
at 1.3V it's marginal, and would need watercooling to be on the safe side.

But remember ... the more voltage you apply the hotter the card will get at load.
But I'm sure you already knew that.