| I would expect it to use multiple cores. I don't use
| Windows or a Mac, but I have system monitoring software
| that graphically shows the load on each core. Typically
| a sharpen operation on a large image takes long enough
| to easily see what actually does happen. On a 8 core
| system about 90 percent of the time is spend with 1
| single core showing 100% usage all of the time, and from
| 2 to 3 other cores being hit repeatedly for short
| intervals. In the last few seconds, which I assume is
| when it puts all of the segments back into the image
| buffer, all 8 cores get hit together for an extended
| period. Extended is longer than the short hits earlier
| in the process, but it doesn't actually last very long
| and the entire process is finished.
|
| Another program uses one single core for the entire
| process.
|

That's an interesting description. So there seems to
be some optimzing of cores, but in a limited way. I
can't imagine it could be much more efficient than that.
Maybe it's true that an image could be broken up for
sharpening, but that would be awkward, and doesn't
seem to be what's happening in what you describe.

| If you had four cores it would not run at half the
| speed. Same two cores, same speed. Just that
| the other
| two cores would be idle.

What I mean is that if you have a 4 GHz CPU with
4 cores then it's 1 GHz per core. With 2 cores it's
2 GHz per core. So it will actually be slower to do
a single-core operation on the 4 core than on the
2 core.