In Windows 7 (x64) there are occasions when I'm running some sort of CPU intensive process like applying filters in Photoshop, etc that take several minutes to run. If I look in the resource monitor I don't see much CPU usage, perhaps 5-10% per core, a few gigs of free RAM, and little disk usage. Obviously the computer is doing work, my question is why isn't that reflected in the stats?
migrated from serverfault.com Aug 21 '11 at 8:46
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If the task is not multi-threaded then it will "bounce" between cores but it will only be able to actually use 1 core at a time. You will likely see that the process itself uses about 25% CPU time on a 4-core processor (i.e. 1 processor fully in use) or about 12.5% CPU time on an 8-core processor.
Showing this kind of CPU usage per-core distorts this CPU usage somewhat as (as I mentioned) the process is does not necessarily always stick to the same core.
Which is what I'd expect to see for a quad-core system running one heavy single threaded task along with some background system tasks.