Some useful info.

Click image for larger version. 

Name:	8800GTS clocks.JPG 
Views:	4892 
Size:	76.8 KB 
ID:	53367

Example: Set 527MHz core speed= you get 540MHz real core speed and 1242MHz shader clock. Set 554 = 567MHz real and 1296MHz shader clock.

Table is easy to read, when you find out the right way

Now just find your sweet spot