Mutli-core Processors: Does each "core" run at the full clock speed or some fraction of the full clock frequency?

Question

Let's say you have a single (1) Intel/AMD x86-64 bit 2 GHz 8 core processor.

Does each of the 8 cores all run at the full 2 GHz or, does each core run at some fraction of the full 2 GHz clock (e.g. 250 MHz)?

Answer 1

Under full load (that is, when you have programs running taking up all available processor time on all cores), all cores will run at the rated speed (eg, an 8-core 2 GHz processor runs all 8 cores at 2 GHz).

Now, it is possible for the cores to be running at different speeds, depending on the actual load:

1. Power saving technology can individually power off idle cores to save energy if load is low (as may often be the case on 8-core machines)
2. Power saving technology can also "underclock" the entire processor to save energy.
3. Intel's TurboBoost and AMD's upcoming Turbo CORE both allow one of the cores to dynamically overclock itself in the very common case where a single thread or process pegs the CPU.

So, in general, the processor will be at the full speed, but it is possible for the speed to fluctuate dynamically.