CW Skimmer - more
- Now that I've proved (to myself at least) that I'm not completely nuts, let
me prevail on your patience with a slightly more complicated question.
Under normal circumstances, I understand that CW Skimmer's own CPU usage
indicator will normally show a somewhat higher number than Task Manager's,
because it is looking at peaks from one application while Task Manager
looks at an average over a second of so of all the processes that are going on.
That being said, I find that there is a pretty logical and explicable
relationship among the Skimmer CPU number, the bandwidth set on the Radio
tab, the number of decoders, and the number of candidate data streams (the
last two are the "98 of 456 decoders" numbers).
Incidentally, it's little-known, but the Sample Rate choice on the Radio
tab *does* affect both the bandwidth covered by an SDR-IQ when used with
Skimmer and (therefore) the CPU demand. To verify this, bring up Skimmer
and change from 48 to 96 KHz. You'll see the CPU loading go 'way up.
Finally, here's the question. Have you ever noticed a situation in which
the CPU utilization of the total of the two Skimmer processes) as reported
by Task Manager is much higher than the CPU utilization being reported by
Skimmer? I see this all the time, but have not been able to figure out
what causes it, or what makes it go away. All I know for sure is that
sometimes something is happening to impose a much higher load on the CPU
for a given number of decoders than is the case at other times. Sometimes
I'll see this as much higher CPU utilization in 48 KHz mode than in 96 KHz
mode. Sometimes I can cause things to revert to normal by changing Sample
rates, stopping and restarting the waterfall, or restarting the program.
One good question that Alex asked was whether it might be a mistake by the
Task Manager. All I can say is that I don't think so, because there is a
definite slowing of other programs when Task Manager says utilization is
over 85 percent, even though Skimmer itself says it is only using 50-55
percent. Moreover, I see the same phenomenon in Process Explorer, which is
a completely separate program - I can't be sure that it doesn't measure CPU
utilization the same way, of course, but it seems to be a stretch, because
Process Explorer was not developed by Microsoft.
Anyway that's the question - if you could, just keep your eyes peeled, or
run some tests, whatever you have time for.
73, Pete N4ZR
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