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[mdettweiler]

Originally Posted by lorgix

I've heard that about X6 before, but I'm not sure it's true. At least where I live, yet.

I was hoping I could save on other equipment because I'm mostly interested in CPU cycles. But what you're saying is essentially that 2*X4 955 is too little for that reasoning to add up?

Are there any particular OS problems associated with using multiple CPUs?

The only reason why 2*X4 995 would not be cost effective is because in order to get two CPU sockets on the same motherboard, you need to buy an expensive server motherboard, rather than a relatively dirt-cheap consumer model. Server mobos can easily run hundreds of dollars (US), but you can get a decent MicroATX (or even ATX if you spot a good deal) consumer mobo for <$100.

As far as OS problems, generally, any "home" version of Windows (XP Home, Vista/7 Home Basic/Home Premium) can only support one CPU. (They're fine with multiple cores on the same CPU, but not with mutliple distinct CPUs.) You need Business/Professional, Enterprise, or Ultimate to have multiple CPUs. This is not due to an actual limitation within the software but rather just because Microsoft doesn't want you to be able to buy a cheap version of Windows for your multi-CPU super computer.

[lavalamp]

To be fair to Microsoft, it's not JUST them, it's sort of a standard industry practice. For example, Sun are also happy to charge licenses for their software based on the number of CPUs.