Reply 60 of 62, by HunterZ
If that's actually blowing the correct direction then you might want to seal the gap between the fan and the mount with something like tape or foam to reduce the amount of air that escapes before reaching the heatsink.
The way your manual is worded, it sounds like they weren't able to actually test 450 & 500MHz CPUs. It may or may not work, and a BIOS update may or may not be required.
Edit: Both of my i440BX motherboards supported 450MHz PII-450 and PIII-550 CPUs, and I'm not sure the manual mentioned the latter.