Unable to boot with all 4 cores active. (QX6850)

[idata]

I recently sold a QX6850 Core 2 Extreme CPU that had been laying around. The buyer claims that he could not boot it unless 2 of the 4 cores were disabled. Does this make sense? It has occured to me that the problem might be in the CPU but that there are other possibilities:

1) the motherboard isn't compatible.

2) the motherboard is defective

3) his power supply isn't big enough

4) the bios isn't configured correctly.

Any thoughts as to what is causing the problem and how can we determine whether or not the CPU is defective?

Thanks

[idata]

All of them are possible. Is an Intel motherboard also use? Details must be supplied. It's like finding a pin in a haystack if there are no additional info given.

[idata]

As I recall there is an option in the BIOS on motherboards that I own that can turn off all but one core, and that is to allow "legacy" OS's to boot. I'm not sure what qualifies as a legacy BIOS, older than Win XP is my guess, since I have never had to use this option. I've never heard of turning off two out of four cores, but who knows what's out there. Otherwise, it sounds like a hardware limitation of some kind to me.