Acording to my laptop website and intel website, my CPU is Intel i5-2410M
Processor Number i5-2410M
Cores 2
Threads 4
Clock Speed 2.3 GHz
Max Turbo Frequency 2.9 GHz
so I have two cores, but why does ubuntu 12.04 show 4 cpus for my cpu ?
It is because of hyper-threading, where each core can (put simply) execute two threads simultaneously Which is why you see 4 threads, 4 threads == 4 'cpus'.
Quoted from wikipedia:
Hyper-threading works by duplicating certain sections of the processor—those that store the architectural state—but not duplicating the main execution resources. This allows a hyper-threading processor to appear as two "logical" processors to the host operating system, allowing the operating system to schedule two threads or processes simultaneously.
