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First, I could not ask this on most hardware forums, because they are mostly populated by gamers. Additionally, it is difficult to get an opinion from sysadmins, because they have a fairly different perspective as well.

So perhaps, amongst developers, I might be able to deduce a realistic trend.

What I want to know is, if I regularly fire up netbeans/eclipse, mysql workbench, 3 to 5 browsers with multi-tabs, along with apache-php / mysql running in the background, perhaps gimp/adobe photoshop from time to time, does the quad core perform considerably faster than a dual core? provided the assumption is that the quad has a slower i.e. clockspeed ~2.8 vs a 3.2 dual-core ?

My only relevant experience is with the old core 2 duo 2.8 Ghz running on 4 Gig ram performed considerably slower than my new Core i5 quad core on 2.8 Ghz (desktops). It is only one sample data, so I can't see if it hold true for everyone.

The end purpose of all this is to help me decide on buying a new laptop ( 4 cores vs 2 cores have quite a difference, currently ).

Gerhard
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  • If you've got multiple beefy programs running, I'd say more cores is gonna be better. But what's wrong with a desktop? –  Aug 27 '11 at 16:08
  • I still have and love my desktop, but I do need a laptop from time to time. This question came up when I read an older article by Jeff Atwood related that points out how the addition of extra cores only help when you're rendering 3d ( or something to that effect ). – Gerhard Aug 27 '11 at 16:20
  • This is a reasonable question, I don't see any justification for thumbs-down. Gerhard it would help if you told us what OS, version, patchlevel you use and whether it's 64-bit. Ditto for the browsers. Also, using a SSD drive for the system disk boosts performance. – smci Mar 15 '12 at 22:43

3 Answers3

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http://www.intel.com/content/www/us/en/processor-comparison/comparison-chart.html

I did a comparison for you as a fact. Here Quad core is 2.20 GHz where dual core is 2.3 GHz. Now check out this comparison and see the "Max Turbo Frequency". You will notice that even though quad core has less GHz but when it hit turbo it passes the dual core.

Second thing to consider is Cache size. Which does make a huge difference. Quad core will always have more Cache. In this example it has 6MB but some has up to 8MB.

Third is, Max memory bandwidth, Quad core has 25.6 vs dual core 21.3 means more faster speed in quad core.

Fourth important factor is graphics. Graphics Base Frequency is 650MHz in quad and 500MHz in dual.

Fifth, Graphics Max Dynamic Frequency is 1.30 for quad and 1.10 for dual.

Bottom line is if you can afford it quad not only gives you more power punch but also allow you to add more memory later. As max memory size with Quad is 16GB and dual restricts you to 8GB. Just to be future proof I will go with Quad.

One more thing to add is simultaneous thread processing is 4 in dual core and 8 in quad, which does make a difference.

Adnan Bhatti
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  • I can agree that a quad is pound for pound better than a dual core, statistically. but once you get that quad laptop, does the overall performance justify the 30% - 40% price diff. , as well as the probable extra battery drain that it might consume under the same situations? – Gerhard Aug 27 '11 at 16:40
  • I have quad core and battery on laptop last barely 3 hours. It is Sony Vaio with top notch quad. I do hate battery life and adding bigger battery cost extra weight. So if you are looking for something in the mid range portability with the punch then dual core will do. As you mentioned you open photoshop time to time... now it really depends how much you use photoshop.. .if you consider it a lot then quad core is the way to go. If you use photoshop few times in a week then dual will do and you will get better battery life. VS2010,Eclipse work equally on both of them. – Adnan Bhatti Aug 27 '11 at 17:14
  • 3 hour usage is very short, that's like gaming consumption – Gerhard Aug 27 '11 at 19:17
  • Using a SSD drive for the system disk boosts performance. And where you put the browser cache(s), and what size they are, and avoiding fragmentation. If there is a separate data disk, is it 720/540/360 rpm? – smci Mar 15 '12 at 22:46
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The problem with multi-processors/multi-core processors has been and still is memory bandwidth. Most applications in daily use have not been written to economize on memory bandwidth. This means that for typical, everyday use you'll run out of bandwidth when your apps are doing something (i e not waiting for user input).

Some applications - such as games and parts of operating systems - attempt to address this. Their parallellism loads a chunk of data into a core, spends some time processing it - without accessing memory further - and finally writes the modified data back to memory. During the processing itself the memory bus is free and other cores can load and store data.

In a well-designed, parallel code essentially any number of cores can be working on different parts of the same task so long as the total amount of processing - number of cores * processing time - is less than or equal to the total time doing memory work - number of cores * (read time + write time).

A code designed and balanced for a specific number of cores will be efficient for fewer but not for more cores.

Some processors have multiple data buses to increase the overall memory bandwidth. This works up to a certain point after which the next-higher memory - the L3 cache- becomes the bottleneck.

Olof Forshell
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Even if they were equivalent speeds, the quad core is executing twice as many instructions per cycle as the duo core. 0.4 Mhz isn't going to make a huge difference.

Casey
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  • what i was trying to gather is, from a developer experience, does it feel faster riding on 4 cores at slightly less clockspeed than 2 cores at slightly better clockspeed? Of course, 4 cores can execute more instructions, but it does not mean they normally do. And even if I did all the math, in the end, what ultimately matters is the tangible user experience using development related apps. – Gerhard Aug 27 '11 at 16:34