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I wanted to know what does 2 cores 4 threads mean about a cpu? I am talking about this cpu which i have

http://ark.intel.com/products/47341/Intel-Core-i5-520M-Processor-3M-Cache-2_40-GHz

I initially thought i5 had 4 cores but i think i am wrong. My understanding of a thread is it is a chunk of code that can run simultaneously(concurrently) with other threads. So, what does 4 threads mean in that specs sheet? Is it different from the programmatic threads. Is the number of threads in there different from the program thread that we create. If it has just 2 cores then is it correct that you can only run 2 parallel programs even though it has 4 threads?

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Once you do some background research on en.wikipedia.org/wiki/Hyper-threading it should make better sense to you. The processor you have does indeed have the capability to do 4 instructions at a time. You should understand that even a single core CPU has the ability to run multiple programs. Its just does NOT have the ability to do 2 instructions at a time. You don't seem clear how on a program actually works. –  Ramhound Jan 12 at 0:08
    
@Ramhound You presumably meant 4 instruction streams. Since the i5 is superscalar it can execute multiple instructions in parallel even from a single instruction stream. Simultaneous multithreading allows thread-level parallelism to be converted into instruction-level parallelism, increasing utilization of execution resources. –  Paul A. Clayton Oct 31 at 19:03
    
I minimized my statement the number of instructions per clock cycle is the difference between a Pentium D and 4th Core i5 minus the size of the die, and the power requirements of course (again simplified) –  Ramhound Oct 31 at 20:21

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Your i5 has two cores, each core can run two threads because of intel's hyperthreading, making 4 threads, beyond that it switches at high speeds between processes. Here's a nice explation of multithreading if you want to know more, but in essence your CPU can run 4 processes simultaniously, and switch at high speed between processes.

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"If it has just 2 cores then is it correct that you can only run 2 parallel programs even though it has 4 threads?" If it has 2 cores the calculation is divide by 2 = parallelism However if you system has hyper threading it can do the 2 calculation in the same core, why, the same core shows to the OS up as 2 cores...logical cores.

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