[non-e-moose]

Silly Rabbit - absolutely accurate times are a security problem. CPU designers (even waay back in Alpha @ DEC) intentionally introduced clock jitter, just to prevent total predictability. For x86, I think if you performed 3-4 of them, and then saved the values in to registers, and then upon completion reported those values, you would find that the time deltas are NOT exactly the same.

[bajsejohannes]

Do you have any sources for this? My googling skills are failing me. I'm surprised early x86 (which I assume you're including) were aware of security issues with accurate clocks; I certainly wasn't until this millennium :D I would rather guess observed clock jitter would be explained by interrupts or some such. Not saying you're wrong, I'd just like to learn more.