xfx 5770 @ 960 / 1365 stable BUT... please read.

GPU = 960 Core / 1365 Memory (46-48 FPS on Furmark Xtreme Test) Max Temps after 20 Min 64C with full load. No artifacts or crashes

here is my question, if i continue to go up in memory on the gpu it seems the fps on furmark is more unstable any thoughts on why? does that mean i am at my max?

960 is the max i could go on ati overdrive, can this be bypassed? should i try for more?

messing with the core voltage on gpus are not the best idea is it?

you can go even higher with a thirdp party cooler i know XFX usually has their own coolers on but take a look at the Artic extreme series. the high temps cause the instability

I run 2 Gigabyte HD 5770SO's in crossfire. I bench them single or crossfire. I find that the different Catalyst drivers act differently on my cards. If you are into it you could try older versions of Catalyst back 3 or 4 versions. If you have updated the drivers over the past few months did you notice a difference? If you try different versions you should clean your registry between installs. My current Catalyst driver version is 8.791.0.0/10.11, it works great and does everything perfectly. I find that 960/1360 is my highest stable clock for benching, above that things get dicey and often result in lock-up. Temperature is not the problem as I have good fan control and the temps are always moderate. Try MSI Afterburner and then edit the msiafterburner.cfg. There is a line that says "unlock voltage control", change that to 1. More volts if your gpu bios allows it. The line below should be changed from 0 to 1.
"UnofficialOverclockingMode = 1"
You should get all the speed you want.

I had a similar problem with my2x 4870 . took me ages to get it working propaly.I think that you will find that putting the right setngs is more important that clocking it. i run a older CCC 10.2 and this is the only one that let me use catalys IA in avanced on crossfire wich took the FPS twice as high as without that setting.

Yep, it pays to try different versions of drivers. The newest isn't always the best. In fact, when I tried Catalyst 11.2, I had to change the video card port I plugged the monitor into. 11.2 and later gave me artifacts(wavy desktop on startup) using the top DVI port on the card. Even going back to earlier drivers I still now use the lower DVI port. For crossfire, the drivers can make a huge difference.

I have a 5770 (asus) and haven't had much luck with stock cooler hitting the magic 1k core mark.. mostly cause of raising the volts created way too much heat. I run at 1.275v and have benched it at 980 core, but the mem clock was next to nothing (trying to get max core). The stats in my sig are what I've found to be the most stable so far, though I haven't tested higher cause this works just fine for now.