mattmartineau88:

Use the latest RivaTuner to get higher clocks

Also, GPU clocks work in blocks. For instance, my 8800Ultra increases in blocks of 27Mhz so if i'm running 648 on the core or 655, it doesn't matter, because the core will only work at 648. I have to incresae to 675 to see the next jump in MHz to 675 etc.

So hit another 13Mhz and you should be at a new 880+ value.