i have a Q. for the overclockers
i have an iMac which has a C2D 266Ghz cpu 775 socket @ 1066 FSB
i may fit a intel 3Ghz C2Q cpu 775 socket @ 1333 FSB

what would be the clock speed of the 3Ghz C2Q 1333 FSB running on a board that is set for 1066 FSB ? ...

any help here would be most grateful ...

What C2Q is it?

A 1066MHz bus is actually 266Mhz quad pumped.
That gives a base clock of 133Mhz x the 20x multiplier of the chip which gives you 2.66GHz

For a 1333MHz bus it'd be expecting to be 333Mhz quad pumped with a 166Mhz base clock. This means the 3GHz chip has a multi of 18 (166x18 = 3GHz)

Either the C2Q would run at full speed (the fsb may well increase on the board automatically) or it's run at 133x 18 or 2.4GHz

Find your motherboard model number and have a look on the manufacturer's website. It should give you a compatibility list, and which bios updates may be required to run certain CPUs.

I have run a 1333 FSB C2D in a bog standard 1066 board, it just underclocked it. Of course, you may be able to manually adjust the fsb to suit your quad or, if the quad is an extreme edition, you can mke up the difference by increasing the multiplier.

thanks for the information ...

Do I read this right - you're thinking of overclocking an iMac? I'd check if there was a model in the same range that ran at the clock speed you're thinking of upping it to. In general, iMacs of each generation were only only sold with a very limited range of clock speeds and Apple make their own main boards, so it's possible the board may only be switchable to a limited set of frequencies, if at all.

Jon

Apple make their own boards for Intel CPUs? I didn't know that.

Yes. Apple is a hardware company, you know. They've always ploughed their own furrow, which is why they can make stuff that "standard" boards wouldn't fit. Make the board fit the design - I bet most big hardware makers would give their front side buses for that ability.

IN the past apple was also prone to soldering the cpu onto the motherboard so you may not even be able to remove the existing cpu.
The Mac Pro cpu's are technically removable but doing so naturally automatically voids the warranty (and apple had managed to get some fairly odd xeon chips without the heat spreader pad that they normally have).