I think you might want to read up on clock domains and rivatuner. All Geforce 6 + series are capable of multiple clock domains but only the Geforce 7 series uses it by default. Also the way the overclocking scales on the Geforce 7 series isnt a per mhz value. Having a 450 core I believe actually scales to 459. The bios only recognises certain clocks and will automatically round them up to the nearest clock domain the bios recognises.
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|CPU: Intel I7 Lynnfield @ 3.0 Ghz|Mobo:Asus P7P55 WS Supercomputer |Memory:8 Gigs DDR31333|Video:Geforce GTX 295 Quad SLIMonitor:Samsung Syncmaster 1680x1050 3D Vision\/Olevia 27 Inch Widescreen HDTV 1920x1080
|CPU: AMD Phenom 9600 Black Edition @ 2.5 Ghz|Mobo:Asus M3n HT Deluxe Nforce 780A|Memory: 4 gigs DDR2 800| Video: Geforce GTX 280x2 SLI