'No context switching' is obviously not true if you run with a standard operating system which will do context switching for all sorts of other things out of your control. So if you have 8 cores each of which support 8 threads, you could have 64 processes running in parallel without context switching. On other processors you may have 2, 4, or even 8 threads. 1 pipeline shared between two processes - this is good when you have more processes, not so good otherwise. But Hyperthreading cuts your execution time by two, even when not using 2 threads! (i.e. With Intel processors, the number of threads is defined by the Hyperthreading which is just 2 (when available). There are two things to take into account now: the number of cores, and the number of threads that can run within each core. I know this question is rather old, but things have evolved since 2009.
