Mac Pro Multi Core CPU usage.

Discussion in 'Mac Pro' started by cyberjunky, Apr 21, 2008.

  1. cyberjunky macrumors regular

    Feb 6, 2008
    Im interested in purchasing a mac pro but im curios about how the multi core technology works with regards to CPU usage.

    1] Does OSX distribute itself over the multiple cores during:
    a) bootup
    b) run time
    [if not then are the cores just for use of 3D rendering/code compilation.]
    2] Will games for windows or OSX (mostly OSX) utilise the multiple cores?

    For the most part i want to run XCode and develop Obj-C, Run freeBSD and some BSD derivatives. I also want to play games on the machine, i do appreciate it is not a gaming machine however i dont want multiple computers in my room as space is incredibly limited so it will be a Mac pro, i just need to know if i got maxed out processor spec would the extra cores actually be used at all?? If they are never ever used because of the way software and/or OSX operates then there isnt much point.

    Thanks in advance guys.
  2. Tallest Skil macrumors P6

    Tallest Skil

    Aug 13, 2006
    1 Geostationary Tower Plaza
    Only certain versions of windows can even utilize dual processors, much less multiple cores. An OS X game will use multiple cores for the most part if it is written to do so.

    And why would you need eight cores to start up? It's about 20 seconds, anyway...
  3. cyberjunky thread starter macrumors regular

    Feb 6, 2008
    Its not that im trying to make some "supa bad" (lol) machine, but theres a lot to factor in. Im just trying to see where it makes a difference and where it does not so that all i know if its only going to do a small portion of what i expect then its not worth the cost. For example if it used any portion of mulitple cores then that might be an indication to me of how OSX will make use of multiple cores for general purpose tasks, OSX already boots fast enough im not really trying to shave anything off of that.

    If i am running a vast array of applications will the workload be distributed by OSX or is that application specific, it would be a shame to be running a cascade of applications and have the first core peak its limit and top out while other cores lie idle if you see where im coming from.
  4. Tallest Skil macrumors P6

    Tallest Skil

    Aug 13, 2006
    1 Geostationary Tower Plaza
    Oh, yes. It's distributed. There was a thread about running two copies of HandBrake simultaneously and they took all eight cores to only about 60%. There's enough power there to choke a horse with enough left over to make its rider clear his throat.
  5. gnasher729 macrumors P6


    Nov 25, 2005
    As an example, if you develop large software projects, XCode will automatically use all eight cores while compiling. That means it can compile eight source files simultaneously. If you have a tiny project with two source files only, it makes almost no difference (but then it takes almost no time anyway). If you have a project with 2000 source files, compiling them will run eight times faster.
  6. cyberjunky thread starter macrumors regular

    Feb 6, 2008
    About using handbrake in multiple instances, did that require specific configurations of either OSX or handbrake?

    So far from what i understand if i unbox the mac pro and do not configure a single thing, i can open every single app in the applications folder and the cumulative workload of everything running across the cores. (assuming there was enough applications and workload to justify that much CPU usage, though lets say it did then from my understanding the cores would not go to waste.)

    I ask these questions because of a couple of things ive read here and there and videos ive seen regarding using an app that came with one of the pros video editing applications (Final Cut Studio maybe), they made a point of the app that comes with it being setup for multi core rendering, which lead me to believe unless you used this specific application everything would be jumbled onto the first core and the rest would be utilised using specific apps if you can see where my confusion came from. However providing the above assumption is correct from what you guys have said i feel a lot more confident that in my understanding of this and believe its a good investment.
  7. Lord Zedd macrumors 6502a

    Lord Zedd

    Oct 24, 2007
    Denver, Colorado
    OSX is designed to distribute the work load across multiple CPUs.

    The hard drive speed is usually the limiting factor on how fast things can work (As in the case of the Handbrake example).
  8. Tallest Skil macrumors P6

    Tallest Skil

    Aug 13, 2006
    1 Geostationary Tower Plaza
    Nope. He just had two Superdrives (two drives, anyway; it doesn't need to be an Apple drive), and he copied HandBrake and opened two of them at once (just name it HandBrake 2 or something).

    In OS X it's distributed. All eight cores are used for all Apple apps. Third party apps will run as many cores as they are designed to see. For example, HandBrake is written to be able to use all eight, but I think CS3 or something like that can only use four.

    Again, it's up to the vendor, but Apple apps know how to make the most of their own hardware.
  9. jamesdmc macrumors 6502

    Oct 17, 2007
    I'm not 100% sure what this means, but it made me laugh out loud.:D

    If you're referring to this thread:, he has "only" a quad-core machine with 4 gigs of RAM and he's getting incredible handbrake performance out of it.

  10. Infrared macrumors 68000


    Mar 28, 2007
    Yes indeedy. Compiling large projects on a Mac Pro is truly wonderful.

    "make -j 8" is your friend :)
  11. jasonvp macrumors 6502a


    Jun 29, 2007
    Northern VA
    Depending on which Apple application you're talking about, they may or may not "know how to make the most of their own hardware." The Final Cut series of video editors, for instance, will not make decent use of all available cores. Oddly enough, QuickTime Pro, will. Why that's the case is anyone's guess.

    I've written this in other posts: OS X has the foundation in place for applications to take advantage of more than one core. In the end though, that's all the OS can really do: provide that foundation. It's really up to the individual applications to make use of that foundation. And in order to do that, the application must be threaded.

    It sounds like Handbrake (never used it) is properly threaded. QuickTime Pro is properly threaded. Photoshop does a decent job of threading as well. Final Cut Express.. not so much.

    Unfortunately, there's no real way to tell whether an application will make good use of all those cores without trying it first. It's not something a vendor will put on a box or package. It's not something you can really look up online (other than reading folks' experiences with the application in question).

    As far as Windows and games are concerned: anything more than 2 cores is a waste. No game that I'm aware of is currently written with threading in mind, so they can't really take advantage of multiple cores. At best, having one core run the game while a second one watches over the rest of the machine is probably all you can expect.


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