7970s are exquisitely
sensitive to memory speed and amazingly overclockable but please make sure it
keeps adequately cooled with --auto-fan! Do it while it's running from the GPU
menu. Go up by 25 at a time every 30 seconds or so until your GPU crashes. Then
reboot and start it 25 lower as a rough start. Runs stable at 1900 memory
without overvolting. Overvolting is the only thing that can actually damage your
GPU so I wouldn't recommend it at all.
Then once you find the maximum memory clock speed, you need to find the sweet
spot engine clock speed that matches it. It's a fine line where one more MHz
will make the hashrate drop by 20%. It's somewhere in the .57 - 0.6 ratio range.
Start your engine clock speed at half your memory clock speed and then increase
it by 5 at a time. The hashrate should climb a little each rise in engine speed
and then suddenly drop above a certain value. Decrease it by 1 then until you
find it climbs dramatically. If your engine clock speed cannot get that high
without crashing the GPU, you will have to use a lower memclock.
What do you think??