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I know that in most cases when you buy a dual-core CPU for the same price you could get a quad-core, you end up getting 2 cores that are faster individually than the 4 cores individually in the quad-core CPU.

Yes, you can essentially have 4 processes run simultaneously with a quad-core as compared to 2 with a dual-core, but because of the aforementioned difference you may find that the dual-core CPU performs better on your desktop machine.

This is in theory of course.

Has anyone tested this? Also, what are everyone's thoughts on this topic?

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13 Answers 13

up vote 12 down vote accepted

Check out these posts from Coding Horror:

Choosing Dual Core or Quad Core

Quad Core Desktops and Diminishing Returns

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Both links go to the same url. Did you accidentally leave out the url for the second link? I'm assuming you were trying to point out 2 different articles. –  Chris Pietschmann Sep 18 '08 at 22:00
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Actually, yes i was! But then, there is a link for the second one from the first one. I'll correct it though. –  Mostlyharmless Sep 19 '08 at 13:56
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Erm... for me they go to different links. Maybe someone already fixed it? –  Mostlyharmless Sep 19 '08 at 13:57

A top notch dual core is always better than a low spec dual core. I found this out the hard way, I bought a laptop with a i7 CPU, it ran at only 2.0GHz, whereas the i5 (dual core) that was available ran at 2.66GHz.

From what I've discovered, I only bought a slow CPU with more cores.

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Depends on the multithreadedness of your apps and how many are running and working. I had a Core 2 Duo and still needed the laptop; but with my Core 2 Quad, I have the first computer that's ever been able to keep up with me by itself. Pure awesome.

Of course that doesn't help with games like Supreme Commander, which insist on pegging CPU 0 and ignoring all the others.

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The Cache may have a major effect, 4 core CPUs tend to have smaller caches (there's only so much silicon) and having more processes running flushes out the cached data you need for a given process.

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Are you saying that quad-core could be slower than a dual-core for this reason?? –  Chris Pietschmann Sep 18 '08 at 21:57

I will never say no to more cores/processors. I can always find something for them to be doing. Besides, I can't notice a difference with my Intel Quad Core versus my Intel Dual Core when gaming; perhaps my video cards mask the difference.

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How often do you have 4 demanding processes running at same time? Or a properly paralelized program taking all CPU? Currently, for desktop PCs, more than two cores are not utilized properly. So, two faster cores with larger cache will be faster than four slower cores.

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you forget that your OS is highly parallelized. –  Darren Kopp Sep 18 '08 at 22:10
    
@Darren...Your joking right? –  user2545 Sep 18 '08 at 22:13
    
Running a virual machine web server for web development? According to the montoriing software, quite often. i7 for the win. –  Fiasco Labs Oct 3 '11 at 3:57

Unless you are a heavy gammer you'll never need that much power ever...
RAM are more useful to a typical (non gaming) desktop PC, seeing that even a webbrowser nowadays can take about 300 megs of ram from a lilttle more than just light browsing.. Typical word window takes up about 20mgs or so but people usually run multiple...
And vista itself is a big hog.. but typically a midline cpu can handle these... even on a quadcore.. usually the program will only strain only one of the cores...

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640K ought to be enough for anybody - Bill Gates –  Daniel May 26 '09 at 23:18
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He never said that. –  Alex Aug 5 '09 at 13:11
    
640K ought to be enough for anybody. Often attributed to Gates in 1981. Gates considered the IBM PC's 640kB program memory a significant breakthrough over 8-bit systems that were typically limited to 64kB, but he has denied making this remark. –  Valamas Oct 9 '11 at 10:25

It depends alot on what you're doing most of the time I think. If what you do involves using several different programs, for example, web development with TextMate, Photoshop, Transmit, Versions, etc., then it might be advantageous to have a different processor able to handle each. If on the other hand, you're only running one program and need it to be able to run fast, like video editing perhaps, you'd probably less, faster cores. At least until more programs are able to make use of multiple cores.

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This is a myth. Having lots of applications "running" doesn't take any CPU time unless they're doing something. If you're rendering a complicated effect in Photoshop and switch to TextMate, you might notice the difference. But TextMate won't slow anything down by itself. –  apenwarr Sep 18 '08 at 22:33
    
@apenwarr: I agree. Having multiple applications running only matters in a scenario like Luke described. superuser.com/questions/19406/… –  Jim G. Oct 22 '09 at 18:24

I have noticed that my quad core box is much faster (wall clock time) in building my large C++ codebases than my dual core box using Visual Studio 2008.

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That's because Visual Studio runs build in parallel. Watch your core usage while building...All 4 will be utilized. –  user2545 Sep 18 '08 at 22:10

I haven't tested this, though I would wonder what kinds of tests would one do to illustrate the difference in terms of performance and responsiveness for developers? How much of the full power of my workstation am I using at any given time? Not that much I think as it isn't like I'm compiling or running tests a high percentage of the time.

My own thoughts are that a dual-core should be fine for myself on a simple workstation setup where memory is a bigger issue for me than the number of CPU cores, as it seems that my browser, ASP.Net worker process and IDE can each take up a few hundred megabytes of RAM that adds up quick. There is also the potential to get a Tri-core CPU that AMD has out that is another possibility for some people.

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Quad core. All the way. It may not be fully usable right now, but everything is trending towards more paralellization, so in a couple years, quad core will trump dual core, and there isn't that much of a difference in price between them right now.

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In a few years, I'll just buy another PC. –  user2545 Sep 18 '08 at 22:10
    
@gfilter.net: Great comment. And I think that's a underrated/underappreciated point of view. –  Jim G. Oct 22 '09 at 18:22

I have eight cores and having so many really does make a difference - no software utilises all eight at the same time, but as a developer with lots going on at any one time (Visual Studio, SQL Server, multiple browsers, a plethora of Windows services, compressing/decompressing archives etc) the benefits are really noticeable. A look at Task Manager will show how all eight cores are being utilised. Performance is far better than on my previous Dual Core.

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I still have to say that even after all this time (almost 1 year after originally posting the question) it still isn't really beneficial to have a quad-core over a fast dual-core. And it'll remain the same until software is rewritten to take advantage of multiple processor cores.

However, I must say that the Intel Core i7 (Quad Core) is really nice in the fact that it is just plain fast. Especially with the memory controller on the CPU instead of somewhere else on the motherboard; this allows for things to run much faster and actually causes the hard drive to be the only bottleneck of the system. But even this cpu isn't fully utilized without proper multi-core software.

It still seems (unless you are doing multi-core programming) it may be better to stick with a faster Dual Core, rather than getting a Quad Core. What I mean "Faster" is a Dual Core that has a faster clock speed per core than the Quad Core. However, the Intel Core i7 is a different architecture than the Core 2, so even the slowest Core i7 (the 920 at 2.6Ghz) is still faster than most of the Core 2 Duo's out there.

If you don't want to buy/build/rebuild a new PC, then one of the biggest things you could probably do today to improve performance with your Dual Core (more than getting a Quad Core) is to get a Solid State Drive to replace your Hard Drive. In almost every system the Hard Drive is the biggest performance bottleneck, and this will help it catch up to the CPU and Ram quite a bit. However, again, the Solid State Drives are still fairly expensive.

In the end, if you have a decent Dual Core that suits your needs, I'd say keep it until a newer multi-core (Quad Core or larger) is more fully utilized by the software you use everyday. Especially since Quad Cores are available Today, buy in the next couple years we are likely to see 8 Cores, 16 Core or and eventually more, and maybe someday ALL of our software will more fully utilize them (I'm looking at you Visual Studio, Firefox and MS Office).

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So the fast, dual-core, i7 M 620 would be the best of the best? :) –  endolith Jul 11 '10 at 20:16
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The quad core i7-720QM would seem to be worse, since it has a lower speed of 1.6 GHz and software wouldn't be optimized for it. Yet it has a max turbo frequency of 2.8 GHz, which is even higher than the dual core. Does that mean it can do similar performance as the dual core when running non-optimized software? –  endolith Jul 11 '10 at 21:31

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