What about hyperthreading?

Hyperthreading is a technology used on Intel CPUs to improve parallelization of computations. A dual-core CPU with hyperthreading enabled appears to the operating system as a four-core CPU. Each physical core powers two logical cores, so in reality hyperthreading does not actually double the CPU’s performance. Hyperthreading is usually enabled in the BIOS by default, and we recommend that it stays enabled, as the SMP cores can use it to process Work Units faster.