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Firefox using 200% CPU on 8-core mac, with NO tabs open

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  • Last reply by india42

india42
india42
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Early 2011 MBP 17", macOS 10.12.1, Firefox 50.0.2

When I open Firefox, the %CPU in Activity Monitor jumps to over 200% immediately (8-core CPU) and jumps higher if I open any tabs. The core temperatures, as reported by iStat Menus, are all over 90° C, even with the fans set to max RPM.

I've shutdown every plug-in, add-on and extension, but the behaviour does not change.

Why is Firefox using so much CPU resource when it is essentially idling? How can I stop this?

Early 2011 MBP 17", macOS 10.12.1, Firefox 50.0.2 When I open Firefox, the %CPU in Activity Monitor jumps to over 200% immediately (8-core CPU) and jumps higher if I open any tabs. The core temperatures, as reported by iStat Menus, are all over 90° C, even with the fans set to max RPM. I've shutdown every plug-in, add-on and extension, but the behaviour does not change. Why is Firefox using so much CPU resource when it is essentially idling? How can I stop this?

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india42
india42 Question owner
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I forgot to mention. There are a lot of threads as well.