No Such Thing as a General-Purpose Processor

The general-purpose processors of today are highly specialized and designed for running applications compiled from low-level C-like languages. They are virtualized using time-division multiplexing, contain mostly predictable branches roughly every seven instructions, and exhibit a high degree of locality of reference and a low degree of fine-grained parallelism. In a modern multicore system, it is fairly common to allocate some cores almost purely to user-space applications, with all interrupts routed away from them so they can run until a scheduler on another core determines they should stop. It is therefore not clear whether every processor in a multicore system needs to be able to run all of the kernel code. Data-parallel algorithms are increasingly run on GPUs. Now that GPUs are cheaper per FLOPS (floating-point operations per second) than CPUs, the trend is increasingly toward coercing algorithms that are not naturally data parallel to run on GPUs. The problem of dark silicon means it is going to be increasingly viable to have lots of different cores on the same die, as long as most of them are not constantly powered.