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What is the difference between a multi-core and single core CPU?

If you had a 1ghz dual core CPU, is it two 500mhz cores or something different?

asked Dec 30 '10 at 13:47

FizzNakLe's gravatar image


A dual core is like having 2 single core processors on the same chip. Each core would have 1GHz in your example (for a theoretical total of 2GHz). But they split the workload between both cores.

Dual core processors have the advantage that they use less power compared to 2 single core CPUs and they work together more flawlessly.

I'm not sure if this is still true with windows 7 (or vista) but xp was only able to use (or only did use) 10% of the second core so you would effectively have a CPU with 1.1GHz. But I highly doubt that this is still the case with 7.

answered Dec 30 '10 at 15:52

Lestat611's gravatar image


edited Dec 30 '10 at 16:05

Thanks! this is exactly the answer I was looking for.

(Dec 30 '10 at 19:12) FizzNakLe FizzNakLe's gravatar image

this answer is not correct, why dont people understand this on this site, "for a theoretical total of 2GHz" no it does not work like that, you cannot add your clock speed to get the result. a single process that is not optimized to use both cores will only use the one core at the 1Ghz. with two processes one running on each core, they both individually run at 1Ghz, this is not the same as the theoretical 2GHz.

(Dec 30 '10 at 22:27) trueb trueb's gravatar image

You missed the point. The question was not about using 1 process on both cores to run simultaneously to execute it faster. That is a totally different question. That is why it's "theoretical" and not "actual" 2GHz.

(Dec 30 '10 at 22:35) Lestat611 Lestat611's gravatar image

not even theoretical... it simply cannot compare it that way

(Dec 30 '10 at 23:24) trueb trueb's gravatar image

Actually, each core would run at 2GHz (assuming this a 2GHz processor). When you get down to it, a multi-processor system with two single-core processors will usually perform better than a single dual-core processor system, due to the way the cores receive their instructions.

(Dec 31 '10 at 10:52) eddieringle eddieringle's gravatar image

yes but you cant add the clock speeds, that is very inaccurate, that is one of the biggest misunderstandings. yes you do see a performance increase on a dual core system, that's why we have them but you dont see double the clock speed. 1 instruction on a single core or dual core system will still take the same amount of time. if i tell a computer to add registers A and B it will still take a nano seccond on a 1 GHz single core or dual core processor.

(Dec 31 '10 at 10:57) trueb trueb's gravatar image

Isn't it like having two cars? If you have two 100hp cars, technically you would have 200hp but you wouldn't be able to go as fast as 1 car with 200hp?

(Dec 31 '10 at 13:21) FizzNakLe FizzNakLe's gravatar image

FizzNakLe - That's not a bad way to look at it actually. Two cars with just as much power but you cant drive them both at once... unless you have another driver...

(Dec 31 '10 at 21:03) trueb trueb's gravatar image
showing 5 of 8 show all

I think that it is two 1 GHz cores. I think that they measure the clock speed of one of the cores.

answered Dec 30 '10 at 14:59

TheTechDude's gravatar image


Multicore processors use less energy than a single core processor with the same theoretical clock speed. I also believe, but don't quote me on this, that multicore CPU's are better at multitasking, but I'll have to look into it to be sure.

answered Dec 30 '10 at 16:23

FilipinoPower's gravatar image



Yes they (dual, triple, quad, and hexa-core CPUs) are better at multitasking. With single core you do not get true multitasking. Multitasking is when 2 things are done at the same time. A single core cannot do this. It can alternate 2 (or more) tasks so quickly that they may seem that they are executed at the same time.

(Dec 30 '10 at 22:17) Lestat611 Lestat611's gravatar image
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Asked: Dec 30 '10 at 13:47

Seen: 5,625 times

Last updated: Dec 31 '10 at 21:03