Reposting this since I realize I posted in wrong location, any help would be much appreciated:
I have managed to get my Radeon HD 5970 up to 800Mhz Core Clock, 1100Mhz Memory Clock and running very stable. But even 25 Mhz more and I crash immediately on benchmarks for MSI Kombuster and 3DMark.
I have tried leaving the voltage alone and increased it by 50mV and to max of 1.1625V in both Afterburner and ATIOvervoltage, same thing, immediate crash beyond 800/1100.
I am on a Alienware Aurora, Intel X58, i7 920 2666Mhz OCed to 3200Mhz, A11 bios, 9gig DDR3. I have tried 11.1 and 12.8 drivers with same results. I have 11.1 running now because it seems to run both card cores better. I've tried the AMD Overdrive and MSI Afterburner with same results as well.
Am I just as high as I'm gonna get or am I missing something?
In my opinion you have reached the threshold of stability. Short of using N2 (liquid nitrogen), you probably will not get much past that.
It depends on the running temps at full load. Give it a voltage bump and it may find stability again, but that is NOT me telling you to do it, just that without raising the voltage you have hit a limit.
Only you can decide what you think is safe and when the returns are not worth it (the risk) anymore.