As far as I know, P3 450 (katmai) are multiplier locked. Surely you will get unstable results if you overclocked it through changing the multiplier. Increasing the FSB will take you maybe up to 500 MHz only. Increasing further will affect PCI devic
Got a Celeron 1G for my P2B with Asus riser card. Was surprised to find out that the new Cely uses new P4 Thermal Solution (large heat sink and fan). Overclocked the FSB to 110 and doing fine for a month now at 1.1Ghz. Mobo temp is 35.