how did you set the 6990 to 600 memory?
MISafter burner.... make sure you've "enabled unofficial overclocking"
Hell i could drop it to 300 right now if i wanted, but it crashes when mining
Hmmm... I'm very puzzled... there have been posts after posts about the limitation of underclocking 6990s
i don't know how you're able to do this. Which 6990s do you have? maybe yours are some particular brand that allows this...
basically i can set the values using MSI AB or whatever other program, but if you actually lookup the memory speed with say GPU-Z it won't run at the specified memory setting. On 6990s, for pretty much most people here, you can only set the memory clock by 125 less than the core clock. ex: 930/805, 940/815 etc... etc...
If I try something like 930/600 with MSI, the core speed will be set at 930 but the memory clock will be at the default setting(1250 i think?) according to GPU-Z...
So, i'm very curious whether you could verify what the actual memory speed is reported at when you down-clock it.