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In what ways are dual-core processors different from single core processor ? Are dual core processors different form multi-processors ? If yes, then how ? What are logical and physical CPUs ?

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closed as off topic by Dennis Williamson, Bart Silverstrim, Adam Gibbins, squillman, Chealion Nov 6 '09 at 23:05

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Is this a homework question? – Amok Nov 6 '09 at 22:08
It Sure sounds like one. – pplrppl Nov 6 '09 at 22:16
Can't I ask qstns which I find curious ? Do they have to be homework qstns alwyas ? I keep getting this comments for many qstns I ask.. – kashyapa Nov 6 '09 at 23:35
Maybe those questions can best be asked in the google search engine or on the wikipedia search engine. They are to broad to be of help to fix a specific issue which is the primary purpose of a site like this. – pplrppl Nov 6 '09 at 23:57
Please use google before you ask such questions. They sound like homework questions because that's what homework questions sound like. Sorry but that's just the way it is. – Huntrods Nov 7 '09 at 6:21
up vote 0 down vote accepted

Dual core processors basically mean that you have multiple (2) processes on the single die. Effectively, it gives you two processors in the one package.

These days Quad core processes are all but the standard and this obviously provides you with 4 processes on the single die. Why would you care? Well the more cores the more CPU performance you're going to get. Historically to get more CPU (processing) power on a machine you'd need to install an faster, entirely new chip or a second processor. These days, given most chips have more or one processor then this is rarely necessary.

"Physical CPUs" refer to the actually physical chips themselves which can potentially contain 1, 2, 4 or even 6 separate cores on the one chip.

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Logical CPUs usually mean how many threads the cpu can seem to run. Like a quad-core could have 4 cpu cores, but with hyper threading, it has 8 logical cpus. Or with Sun Sparc CPUs you have 8 (or was it 16) logical cpus per physical cpu core. – Raynet Nov 6 '09 at 23:08
The basic facts here are right -- a dual core processor has essentially two processors in the silicon die inside the chip, and the workload that would normally be managed by one processor is usually load-balanced between the cores available. However, the analysis is a bit off. The extra cores don't always lead to extra performance, though they can, and this is a software problem that's improving all the time as new software comes out. Also the idea that upgrades aren't necessary because you have extra cores is wrong. Upgrades just scale out (extra workers) rather than up (a faster worker). – Lee B Nov 7 '09 at 0:34

logical example

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A Dual Core processor is a multi-core processor with just two cores.

A dual-core processor running at 2GHz will not give you the same performance as a single-core processor running at 4GHz but it will run much cooler. It is the physical limitation of exponential increase in power with speed which has forced processor manufacturers to resort to multi-core technology.

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Why the down-vote? – simplr Nov 6 '09 at 22:29
I have to disagree that single core processors are more efficient, multi core processors will be just as efficient as single core if the code isn't multi-threaded, if it is then they are much more efficient. – Zypher Nov 6 '09 at 22:29
@Zypher: Can you point me to any benchmark test that will show that? Remember, I compared single-core at 4GHz to a dual-core at 2GHz. Obviously two cores each running at 2GHz will be better than one core running at 2 GHz. – simplr Nov 6 '09 at 22:35
@simplr: you're making a false comparison. These days, manufacturing is running into clock rate barriers, not core barriers. So you can generally add more cores at the same speed. This is faster processors are made these days. – Graeme Nov 6 '09 at 22:51
And we must not forget the old Intel dual-cores that were basicly just two single-core cpus glued to the cpu. And a current multi-core CPU is probably very efficient in single-core mode as all the L2 or L3 cache that was shared and consumed between all the cores is now fully in use of the one core. – Raynet Nov 6 '09 at 23:04

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