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When I bought my Lenovo Thinkpad 520, it had Windows installed. I promptly cleaned that out and installed Fedora 16. I recently visited the /proc/cpuinfo and, much to my surprise, discovered that it has four CPUs listed (0-3). I do not remember asking for extra CPUs when I got it, believeing I was getting only a single processor. Could this be a mistake in the cpuinfo file?

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Most likely you have a (single) i5 processor: two cores + hyperthreading = 4 CPUs – don_crissti Mar 8 '13 at 0:03
Flag for SuperUser? – user34080 Mar 13 '13 at 1:23
@ColeJohnson Er. Why? – Michael Mrozek Mar 13 '13 at 1:30
@Michael it's not really Unix specific. Sure, the program is, but this could also affect a Windows system if the program was poorly coded. – user34080 Mar 13 '13 at 1:45
up vote 8 down vote accepted

From the T520's specs:

Intel® Core™ i5-2520M processor (dual-core, 2.50GHz, 3MB Cache),

The i5-2520M has 2 cores + hyper threading, for a total of 4 cores seen by the system.

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You probably have one processor with two cores and hyper threading technology. The hyper threading doubles the reported CPUs.

2 cores + hyper threading = 4 reported CPUs
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