I recently aquired a powercolor 7990 to play with. With the factory BIOS It was an ok card. Powerful to say the least, However Overclocking was decent. From a factory core clock of 900mhz, the maximum speed I could make a successful 3dmark 11 pass was 1080. With my 3930K at factory default speed, and memory at 2133, this achieved a score of around 14500
During PDXlan 22 In portland Oregon, Powercolor had a booth. I was able to inspect my AX7990 against there Devil 13. Visual Comparison suggests that Both card are identical, the devil 13 having a red fan shroud vs my all black card. I asked the reps if there was any other difference, and they said just clock speeds and some more aggressive bios settings. This hardened my belief the cards were identical other than the bios.
I acquired the devil 13 Master, and Slave bios and Used the newest ATIflash to flash both the slave and master bios with the corresponding devil 13 bios. Success. Both bios flashed correctly and the system booted into windows. Windows detected new hardware and installed drives as if I had installed a new card. I expected this. I had originally flashed the bios in an attempt to unlock the voltage adjustment of the AX7990 because forum posts suggested the devil 13 had unlocked voltage control. I was disappointed to find that this DID NOT unlock my voltage control Afterburner. What it did do was set my default gpu core clock at 1000mhz. I decided to begin Overclocking tests regardless of voltage control to see if the bios settings were in fact more aggressive, AND THEY WERE. I quickly found that I could MAX OUT the sliders on both the GPU core and memory. This resulted in an Overclock of 1125 core and 1575 memory. 3dmark 11 resulted in a score of over 16000.
Forgetting to reset the Clock speeds to default, I realized that I had been gaming with the clock sliders maxed out for 3 days straight with no problems. I am now playing Bioshock Infinite with the clock sliders maxed with no problems what-so ever.
I will post benchmark screenshots soon.