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One really powerful core vs Two mid range cores

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May 24, 2011 10:13:56 PM

What would be the performance be, if you had two identical 3ghz Pentium dual core processors, and the one was clocked in half to 1.5ghz while the other one stayed at 3ghz but had one of it's cores disabled making it a like a uni core. How would the video encoding performance be if the program was optimized for both uni and dual core processors.
May 24, 2011 11:29:32 PM

I would think that the one still using both cores would be better. Instead of having all the processes solely working on one core. Idk why you would want to do that tho
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May 24, 2011 11:35:27 PM

Core scaling usually isn't perfect, but having one processor do everything(background tasks and whatnot) also slows it down. I guess it depends on which pentium dual core you are talking about. If one has L3 cache shared between both cores, then the 3ghz single core would be able to utilize the entire L3 cache thus probably giving it the edge over the two sharing the cache.
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May 25, 2011 12:04:37 AM

I wouldn't do that, I just used the Pentium as an example. Cause Intel makes single and dual core atoms, and thought it would be better instead of Intel making a dual core atom just make the single core atom more powerful while keeping the power usage around the same as the dual atom.
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May 25, 2011 12:09:49 AM

shafe88 said:
I wouldn't do that, I just used the Pentium as an example. Cause Intel makes single and dual core atoms, and thought it would be better instead of Intel making a dual core atom just make the single core atom more powerful while keeping the power usage around the same as the dual atom.

Power is exponential while speed is linear for one core.

Adding in performance features for one core increases its power use more than its speed. Thus two lesser cores would be able to beat it in the same power envelope.

This is the same as frequency. A 1.5ghz single core Atom will probably use the same amount of power as a dual 1ghz Atom thus the dual core is more efficient.
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May 25, 2011 12:14:01 AM

The issue is that stronger CPUs mean that they have longer pipelines or very high clock speeds, longer pipelines mean very long delays if there is an incorrectly predicted path, higher clock speeds require better transistors and will lead to greater power consumption, netburst was supposed to make it to 10GHz and be a super processor with its crazy long pipeline, but due to heat restrictions and path prediction challenges netburst got killed off in favor of more cores simply because you can strap two full sized cores together and clock them about two thirds of that you can run the single cored unit at giving you more performance in a slightly larger thermal envelope.

Ideally one super super fast processor would be best, however its just not technically feasible so we opted for multiple cores.
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May 25, 2011 12:24:19 AM

hunter315 said:
The issue is that stronger CPUs mean that they have longer pipelines or very high clock speeds, longer pipelines mean very long delays if there is an incorrectly predicted path, higher clock speeds require better transistors and will lead to greater power consumption, netburst was supposed to make it to 10GHz and be a super processor with its crazy long pipeline, but due to heat restrictions and path prediction challenges netburst got killed off in favor of more cores simply because you can strap two full sized cores together and clock them about two thirds of that you can run the single cored unit at giving you more performance in a slightly larger thermal envelope.

Ideally one super super fast processor would be best, however its just not technically feasible so we opted for multiple cores.

Isn't there a small delay for a core if it has to stop and switch to a different task? Wouldn't dual cores at least be better than that?
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May 25, 2011 1:17:16 AM

Yeah context switches do incur a fairly large penalty since things need to get moved from the registers all the way back to the main memory and then the new stuff needs to get loaded in so multiple cores would help if you were running multiple programs.
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