I understand that CPU utilization is 1 minus the proportion of some recent span of time that the CPU is idle, as explained here:
The answer to this question may be obvious given that definition, but does this mean that CPU utilization numbers will be bigger (given the same amount of work to do) when the CPU is throttled down?
(Note that I think this matters because people open Task Manager or System Monitor and interpret CPU utilization values as evidence of workload intensity.)
Yes, given the same amount of work, running on a CPU at a lower frequency would result in higher utilization, since the CPU must spend a longer time in the non-idle state to complete the work.
This is all quite complicated to interpret in systems with multiple cores, which may be throttled at different rates, and where some cores may be active while others are idle, but that's the general principle.
As you point out, this is one reason the CPU utilization is only an approximate measure of a workload's CPU intensity. Other reasons include the influence of caching, context switches, competition for shared resources, etc.
