Originally Posted by Murlocke
If your driver crashes (heaven crashes) then you need to restart your entire computer. This is why many people are claiming "I can do +170/+500 but its slower than +150/+500". I've tested it thoroughly and even resetting Precision does not fix it.
I can easily do +190/+500 in heaven stable for at least 5 loops after a driver crash. After I restart my computer heaven will crash instantly and I have to go back down to +135/+500. This is why i'm taking all these +155 to +200 results with a huge grain of salt. I'm looking at their FPS and it's low compare to mine, which leave me to believe they are not restarting their comp after each crash. Even though the card says it's being utilized to 100%, it is not.
Look at FPS in heaven, crash driver, then look at it again. It will be 5-10FPS lower until you restart. Not a full load on the card = unstable overclocks become stable.
I will be adding this to the OP in hopes to get more accurate overclocking results. This is also why we keep hearing people saying "lowering the TDP results in better overclocking" and "keeping the fan above 65% results in better overclocking". It's because there driver crashes prior to changing it, so they assume (like I did) that the change improved overclocking.
Yes, the cards do not operate properly no matter what you do until you reboot. The max I can run Skyrim at in SLI is 120/350 for any length of time. Not sure if SLI is dragging my numbers down quite a bit versis single card but if I go over those settings one of the cards will drop down to default and the game almost crashes.
I have found Skyrim at 2560x1600, everything maxed, 8x MSAA, 16 AF, Ultra settings, FXAA, hi-res texture pack loaded will crash my SLI setup way before Heaven or any other game. Although the FPS is still very impressive, I get 100-150 FPS with these settings running around the world.
Amazingly when the VRAM counter states 2100 MB used I don't get any slowdowns.