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I have found both Safari and Firefox use a very high amount of CPU during downloads (>200% CPU usage), can anyone explain as to why this happens? It occurred both before and after a complete system reinstall. It also uses the same amount of CPU despite download speed. I am using Mac OS 10.8.

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I also had images of Firefox doing the same thing, but accidentally deleted them during the reinstall.

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Uhh so it's using 260% of the CPU while downloading? That seems impossible. :) –  Ƭᴇcʜιᴇ007 Sep 19 '13 at 17:24
hence the question :) Does a higher then 100% percentage mean it is using multiple cores for that process? –  user2210274 Sep 19 '13 at 17:25
I'm not an OSX user so I can't say for sure, but in the Windows world, no, the CPU Percentage is 100% max (1 busy core in a 2 core system would show 50% use for example), and I would expect the same from any modern OS -- but again I don't know for sure. That's why I commented on it. It seems crazy, but I have no answer. :) –  Ƭᴇcʜιᴇ007 Sep 19 '13 at 17:28
I see, so it should be averaging the cores. That it is. I've had a problem along these lines with QuickLookSatellite as well. superuser.com/questions/617658/… –  user2210274 Sep 19 '13 at 17:29
Activity Monitor (or top or ps) doesn't "average the cores", so 200% means 100% for two cores. –  ؘؘؘؘ Sep 19 '13 at 22:55

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