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I have a new System76 Gazelle laptop with an Intel i7-3820QM CPU. My understanding was that this chip was a quad-core. If so, why does system monitor show 8 cpus?

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Because this CPU is equipped with Intel® Hyper-Threading Technology, this means that for each physical core you get 2 logical thread, 4 times 2 is equal to 8.

http://ark.intel.com/products/64889/

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I've been in the AMD world for a long time. Does this stuff really make a difference? I get the sense my new "logical threads" will have half the horse power of a normal thread and I'd be better of without it. –  HDave Jul 30 '12 at 21:50
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@HDave - hyperthreading is just a way of abstracting task switching away from the OS and down into the processor. Whether or not it helps or hinders depends greatly on your workload, but there's very few situations where it hinders. I wrote an answer on Super User about it a while ago here: superuser.com/questions/96001/… –  Mark Henderson Jul 30 '12 at 21:53
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no, HT is a good technology, you can experience poor performance with some software that is not optimized for multi-core or multi-threaded environment, but for what you can get today is always good to have it. –  user827992 Jul 30 '12 at 21:57

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