On Fri, 2009-01-16 at 16:44 +0000, Ian Thompson-Bell wrote:
What you have there is a Hyperthreading CPU, which essentially supports two threads on the same processor therefore it looks like two cpu's from a software perspective.
The actual reason behind this (not the marketing reason) is that the execution pipeline on the Prescott series of CPU's was rather long which increases the chance of a cache miss where with a single thread your execution unit would be sitting idle..with two it has something to do.
Benefits vary and of course depend on an SMP aware kernel, there are also distinct kernel modifications that make up the difference between really having two processors and just being able to time slice between two simultaneous threads at a hardware level. But I will let you and google find them :)