[dspillett]

This is the sort of factor that people forgot to include when testing SSDs for power/performance metrics in the early days of them being within reach of the average home users. An SSD (especially some of the older models) can pull more power than a good spinning metal drive when running as full force, but what some people didn't factor in was that the SDDs did more in a given time especially with latency sensitive workloads - so to do the same work as the traditional drive it would need to run at run pelt for far less time meaning quite a saving in power.

Another thing modern CPUs do as well as slowing down when under light load is to almost turn parts of themselves off when not needed. These are things that any CPU could potentially do though, it isn't a difference between CISC and RISC designs.