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adventure : Scoobydoo: Episode 2 The sequel of Scooby and Sammy's adventures. Same principle as in the previous episode (available on this website). Click on "Instructions" to see...
crazy : Xiao Xiao 7 A great fight scene from the animation movies Xiao Xiao.
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Part 2: How Many CPU Cores Do You Need?

1:30 PM - 08/03/2009 by Don Woligroski

A few months ago, we looked into the effectiveness of using different numbers of CPU cores with various types of software. We received a lot of good feedback from that article, and there were some interesting suggestions from the community that we've taken to heart in this follow-up.

Primarily, there was a concern that part one might have been flawed technically, as the Core 2 Quad Q6600 we used in our testing does not share all 8 MB of its L2 cache between its four CPU cores. Intel's Q6600 instead has two separate 4 MB cache repositories, each shared between one pair of CPU cores. This means the quad- and triple-core results would have demonstrated the CPUs utilizing 8 MB of total cache, while the dual- and single-core results show that they were likely benefiting from 4 MB. Indeed, the benchmarks may have been reflecting the difference in L2 cache availability more than performance attributable to enabled processing cores.

To remedy this, we are using a different CPU this time around: AMD's Phenom II X4 955 BE. There are a number of reasons why the Phenom II is ideal for these tests. First of all, its 6 MB of L3 cache is shared between all four CPU cores, so the cache's impact on results will be kept to a minimum. Secondly, since there are now X2, X3, and X4 versions of the Phenom II CPU based on the same die, we will have the opportunity to test the validity of the method we use to simulate fewer CPU cores. By comparing simulated results to an actual retail CPU with fewer CPU cores, we will know more definitively whether disabling CPU cores in the operating system is a truly legitimate test.

At the end of these tests, we will be able to compare the Phenom II X4 results with the ones achieved by Intel's Core 2 Quad Q6600 to see if the impact of shared CPU cache is dramatic or minimal.

A few readers were also interested in simulating a scenario where multiple applications are running at the same time, in order to gauge the benefit of additional CPU cores while multitasking. We therefore ran a new test to analyze this type of scenario, too.


Talkback
erdinger 08/03/2009 7:44 PM
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Very intresting article,now I'm even happyery I bought a Phenom II 720 for my gaming rig!

icepick314 08/03/2009 8:00 PM
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"In any case, there are two lessons to be learned here: first, try to avoid a virus scan during your gaming sessions."

what kind of PC gamer does virus scanning while running a game?

KyleSTL 08/03/2009 8:06 PM
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Why no power consumption testing? I was a little curious what disabling cores in the OS would do to power consumption under load. A little let down, but otherwise good article. It's good to see a scaling article at least yearly since people refer to the dual/quad debate so often and often the tests that were run within article that are referenced are out of date and irrelavent.

jtt283 08/03/2009 8:24 PM
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Good article, and very interesting.
Now I really hope I can unlock the 4th core when my 720BE arrives (hopefully later this afternoon), but I won't sweat it.
Did you happen to test if it made a difference what scan priority was set in AVG? I'd really like to see those numbers.

Anonymous 08/03/2009 8:31 PM
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So, how did you manage to get an Nvidia-based graphics card (Gigabyte GV-N250ZL-1GI 1 GB DDR3 PCIe) up and running with the ATI Catalyst 9.6 drivers?! ;-)

Besides that bit of confusion, thanks for the benchmarks!

1word 08/03/2009 8:32 PM
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very happy with my 720 BE. I constantly check with the activity on the cores, and many many apps use all three cores, or multi- tasking uses all the 3 cores. some activities like defrag uses only 2 cores. image editing software, and general applications like browsers, office apps use all three cores, especially when multi tasking.

i'm very happy with the AMD 720BE.

jcknouse 08/03/2009 8:34 PM
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KyleSTL :
Why no power consumption testing? I was a little curious what disabling cores in the OS would do to power consumption under load. A little let down, but otherwise good article. It's good to see a scaling article at least yearly since people refer to the dual/quad debate so often and often the tests that were run within article that are referenced are out of date and irrelavent.



I liked the article well, but I was too finding myself asking "What was more power efficient? the PII x2 550 BE or the PII x2 955 BE?

Would love to know, even if it was just that you guys just happened to glance at a P3 Kill-a-watt or some other meter you had inline during testing or something.

Thanks for great work, guys :)

erichlund 08/03/2009 8:36 PM
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It's true that an application like iTunes does not benefit from multiple cores, when run without any other apps. However, it also doesn't compete for more than one core when multiple apps are running, so single threaded apps also benefit from multiple cores when users are multi-tasking.

What one really needs to know with iTunes and it's competing applications is: Which one competes most efficiently in a multi-processing environment? In other words, which uses the least resources while performing essential tasks, leaving the most resources for the other tasks being performed? To say it in perhaps the clearest way, what applications play well with other types while multi-tasking, and which hog resources, making it more difficult to multi-task?

That's not really the point of this test, but it may lead to some interesting future evaluations.

jtt283 08/03/2009 8:48 PM
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^Yes, that's why it would be interesting to see if (and how much) the impact varied if AVG was set to slow, normal, or fast for its scan priority.

Paranoidmage 08/03/2009 9:01 PM
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erichlund 08/03/2009 9:20 PM
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paranoidmage :
You shouldn't test the games at 1024x786 at low details. These benchmarks are supposed to simulate actual usage. No one will actually run games at that resolution and detail unless their computer is a dinosaur. If you want to remove bottlenecks, use a better GPU like a 4890. How do I know if multiple core will actually help me? I run games at 1920x1200 with med-high details.


That was not the point of the test. They only really wanted to understand the scalability of multiple cores, so taking the graphics out of the equation helps. We see that multiple cores helps the games.

You can do this same thing with your game of choice. You can set your OS to run the game with different numbers of cores, and see how you games are impacted at your chosen resolution. They've given you the technique, just apply it.

We now also understand explicitly (what we already implicitly understood), that we should run games by themselves, because background processes will impact our performance (there's a duh in there somewhere).

The work they've left on the table is for application users. Picking the right set of applications that work well together in a multiprocessing environment could be interesting. For instance, does Sun's Open Office, originally developed as Star Office in a Unix multiprocessing environment, scale better than MS Office? Which is more heavily impacted by background processes? The fact that's it's free (assuming you have the ability to download it) is an added benefit, but not directly the issue.

2shea 08/03/2009 9:22 PM
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if you go and use a high res then the results will depend far more on the gpu rather than cpu, which is what is the core of this article... If they do it at low level then it will be done at high level because high level details depend on the gpu far more.

masop 08/03/2009 9:29 PM
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Great article. The benchmark results with avg running alongside wic are interesting. Although I don't have virus scans running while I do my gaming, I do have a crap load of apps and utilities running on my system at any given time, most idle, but still occupying resources. I think it is about time to upgrade my dual core to a quad setup. Aside from trying to justify the upgrade costs to my wife (LOL) and not get murdered in the process, I'm considering it all but done, hehe.

chaohsiangchen 08/03/2009 9:36 PM
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For gaming performance, Tom's should also use games that support quads such as GTA4, HAWK, FarCry2 or Empire:Total War. Other review sites has shown that games optimized for quads perform better with more cores than higher clocks.

volks1470 08/03/2009 9:45 PM
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yea, my 720BE @ 3.6GHz + a GTX 295 works pretty well with Crysis. I just wish the damn processor would overclock to 4GHz, but I just can't on air :(

Cleeve 08/03/2009 9:46 PM
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paranoidmage :
You shouldn't test the games at 1024x786 at low details. These benchmarks are supposed to simulate actual usage.



The problem with that is, the graphics card will bottleneck the results far more than the CPU cores, so we won't learn as much by high-res testing.

With low-res, we know where the number of cores becomes a limitation.

Cleeve 08/03/2009 9:47 PM
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bogan :
So, how did you manage to get an Nvidia-based graphics card (Gigabyte GV-N250ZL-1GI 1 GB DDR3 PCIe) up and running with the ATI Catalyst 9.6 drivers?! ;-)



Ouch! Thanks for pointing that out, fixed!

Cleeve 08/03/2009 9:53 PM
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jcknouse :
I liked the article well, but I was too finding myself asking "What was more power efficient? the PII x2 550 BE or the PII x2 955 BE?Would love to know, even if it was just that you guys just happened to glance at a P3 Kill-a-watt or some other meter you had inline during testing or something.Thanks for great work, guys



From the glances I took, the Phenom X4 used more power than the X3 at the same frequencey, even if the OS was only using 2 cores. So in my mind there wasn't much of a story there, but it was shortsighted of me not to share that in the article.

Good suggestion though, next time I look into this I'll definitely supply some formal power usage charts...

Proximon 08/03/2009 9:53 PM
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Hopefully we can do the same for Windows 7. Great article.

Aerobernardo 08/03/2009 10:12 PM
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Amazing article.

I would just like to point out that one of my concerns about having less then 4 cores is the scalability/performance with Xfire or SLI. That point is missing on this article, but I do believe it's just a minimal result that is not hte focus fere.


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