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I'm really confused.

What determines the speed of the CPU/processor?

Some compared a dual core with 2.8ghz and a 2.4ghz quad-core and say the quadcore is better.

But when it comes to a dual core with 2ghz and a 1ghz quad-core processor, the dual core wins the comparison.

What really determines the performance of the processor?

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2 Answers 2

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Here is where the problem with multiple cores comes in to play. How do you define "speed" and "performance"?

Speed would most likely be the clock rate that the processor works at but, like cars, two cars that travel at the same speed (70 mph) may have wildly different "performance" as in one may manage a much higher miles per gallon and thus be more efficient at that speed. A current generation 2GHz i7 CPU would likely make a 3GHz or better Pentium 4 look slow.

With multiple cores performance is almost impossible to quantify and depends on the task you are running. Multiple cores may allow more tasks to be done, but unless those tasks are written to make use of multiple CPUs then there will be little immediate gain in performance. Programs are beginning to make more use of multiple CPUs but they are still relatively uncommon as most tasks do not actually need them.

In my experience the main benefit of multiple cores is responsiveness and usability when working in demanding situations. One program may be working hard doing it's job, but while that's going you can be getting on with something else with little to no loss of that high performance "no lag" feeling.

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To go to the very basics, the number of cores is the no. of tasks a processor can do at a single time, and the clock speed is how fast it can do them.

Now, a 2.4Ghz quad core will be faster than a 2.8Ghz Dual core if the task can be split into 4 parallel tasks

Performance is a mix of processor generation, no. of cores, cache, clock speed and many other factors.

Hyperthreading is when a single core processor has some extra hardware which lets it behave as a dual core for certain tasks.

Multithreading is when a Program makes use of multiple threads to do its work

There arent CPU's in a core.. there are cores in a CPU

I'm assuming that the processor architecture is same..
A 3Ghz Pentium D vs a 3 Ghz i3 -- the i3 would win (thanks to sidran)

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hmm question... why does my friends dual core has 4 cpus??? he saw it on the task manager –  user913233 Sep 3 '11 at 13:46
    
That would be Hyperthreading –  Akash Sep 3 '11 at 13:46
    
The clock speed isn't really how fast it can do them. A 2.4GHz quad core might still be faster than a 2.8GHz dual core for single-threaded tasks if at each clock, the first CPU can do more than the second. Clock speed is only comparable within the same architecture. –  Ben Richards Sep 3 '11 at 13:49
    
Yes, I'm assuming its from the same architecture.. thats why I mentioned "to go to the very basics" –  Akash Sep 3 '11 at 13:50
    
what is hyper threading? is hyper threading possible on my amd v105 processor 1core? –  user913233 Sep 3 '11 at 13:54

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