6990x2 safe overclocking

[Sjalq]

I need some input on overclocking the very expensive things on my desk.

1.Have any of your ever blown a card while mining by following only tame overclocking procedures (switches included on the boards, catalyst settings etc)?
2.I want to set the BIOS OC switch on the 6990s to the 450W setting. What have been your experiences?
3.I want to set the power consumption up by 20%. What have been your experiences?

[Genrobo]

don't be a wussy
just overclock the crap out of them

[Forp]

I just started mining these days and am a n00b - but I had an interesting phenomenon on my first day you might consider useful.

For some stupid reason i let a piece of plastic sit on the top of my 6990 - and some minutes later rectangular shaped parts of the screen went black. Temp was at 85 Celsius. I turned off, let cool down and restarted. The areas where back again.

I assume it was a partial memory failure... :-(

 

[Sjalq]

don't be a wussy
just overclock the crap out of them

lol, like

Anybody else have inputs?

[xen82]

What was the limiting factor for me was cooling. With a big external fan blowing on the cards (2x6990), I was able to do 905 MHz and 625MHz underclocked memory (using MSI Afterburner, couldn't get it down unfortunately to ~300MHz), and it was running somewhat stable.

On my other box (TJ07 case with 2x 6990s running 11.04) I had to drop my clock speeds to 830MHz with 294MHz underclocked ram due to case cooling issues. I'm looking at consolidating all my 6990s in one box and using some proper water cooling to keep things running cool. At that point 925+ should be easily attainable.

The thing is you don't want the card's temperature nannies to kick in. If they do, you suffer a bigger performance hit than running at a lower speed. I think it's safe to run the cores up to 96C.

[Sjalq]

What was the limiting factor for me was cooling. With a big external fan blowing on the cards (2x6990), I was able to do 905 MHz and 625MHz underclocked memory (using MSI Afterburner, couldn't get it down unfortunately to ~300MHz), and it was running somewhat stable.

On my other box (TJ07 case with 2x 6990s running 11.04) I had to drop my clock speeds to 830MHz with 294MHz underclocked ram due to case cooling issues. I'm looking at consolidating all my 6990s in one box and using some proper water cooling to keep things running cool. At that point 925+ should be easily attainable.

The thing is you don't want the card's temperature nannies to kick in. If they do, you suffer a bigger performance hit than running at a lower speed. I think it's safe to run the cores up to 96C.

What I also find interesting is that ATI's default setting allows my cards to heat up to about 100C. Wonder why they did that?
So your thoughts on default cooling, 450W and 900Mhz?

[Jack of Diamonds]

If you can keep ambient temp at around 23-24c or less and card temp at under 80c 24/7 go for it.