I have a BFG GTX260 OCX. The clock on the right is displayed at 655 which is correct but on the graph it only goes up to 648 during gaming. Why is that? I'm not overcocking. Everything is at default speeds.
Because you cannot set it to 655.
Keep reducing/raising the clock speed and you will see it jumps, it does not change 1MHz at a time.
Thats the way it was designed.
(I had a quick go with Rivatuner to see how much it jumps and found it to be inconsistent at times which is strange as I have not seen it behave that way before, but the premise still stands)
For example, if I dial 674MHz, it sets to 675MHz and will remain there until I set at 681 or just above, then it changes to 684MHZ, which remains until I set 688MHz when it jumps to 691MHz.
Just know that it jumps.
If you want to work out exactly how much, experiment.