Intel iMac, quartz beam synchronization and xbench

Discussion in 'Mac Pro' started by plinden, Feb 19, 2006.

  1. plinden macrumors 68040

    plinden

    Joined:
    Apr 8, 2004
    #1
    First, let me state that I'm one of those who's dismissive of synthetic benchmarks, more interested in how a computer works in real life. But one of the disappointments with the Intel iMac was the lower than expected xbench results, especially considering the better than expected xbench results from the Intel developer systems.

    So while reading arstechnica, I recently came across a reference to this on macintouch: http://www.macintouch.com/readerreports/imacintel/topic2074.html :
    I decided to try this out, downloaded xbench, and got the results in the attachment. To summarize, with beam synchronization enabled, my results were pretty close to what others get. Comparing with xbench after disabling beam sync, most results were close enough to being identical, but the Quartz graphics test went from 65.45 to 116.78, and the UI test went from 21.22 to 244.92. My overall score almost doubled from 54.94 to 90.38.

    Now, like I said, I'm not interested in the synthetic benchmarks, and I'm not going to permanently disable "beam synchronization" (whatever that is) just for bragging rights, but does anyone have any insight into what this means for the UI? Does this "even up" the comparison, or is this just adding a new synthetic parameter?

    Anyway, although I'm not interested in the actual figures I get from xbench, any ideas on how to increase the Random Uncached Write figure?
     

    Attached Files:

  2. jared_kipe macrumors 68030

    jared_kipe

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    Seattle
    #2
    Awesome, Let me try....

    EDIT: Where the hell is that, can it be done by terminal?
     
  3. plinden thread starter macrumors 68040

    plinden

    Joined:
    Apr 8, 2004
    #3
    You need to install xcode from the installation DVD, then you can access it from Finder, <your HD>/Developer/Applications/Performance Tools/Quartz Debug. Enter Command-B and disable Beam Sync
     
  4. mkrishnan Moderator emeritus

    mkrishnan

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    Grand Rapids, MI, USA
    #4
    So does anyone know what beam synchronization actually *is*? :)
     
  5. stoid macrumors 601

    stoid

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    So long, and thanks for all the fish!
    #5
    I thought that had something to do with quantum mechanics... Has Apple jumped too far ahead of their time again? :p
     
  6. plinden thread starter macrumors 68040

    plinden

    Joined:
    Apr 8, 2004
    #6
    I'm hoping someone can answer that, but I've read over the Apple tech note referenced in the quote a few times and let it sink in. One part says:
    I'm guessing, on no evidence, that xbench is affected by the first item, ie. it is trying too hard to draw and flush the display.
     
  7. jared_kipe macrumors 68030

    jared_kipe

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    #7
    Beam sync has to do with how closely the operating system monitors how the screen changes. The only side effects to turning it off is MAYBE some tearing, and video artifacts with video clips. Most people don't see anything when they turn it off. I don't know if it really affects real world speed either though, but it sure helps the open GL tests. I think Xbench just needs to be coded a little better.

    EDIT: I'm pretty sure its also called Vsync for PC terms.
     
  8. plinden thread starter macrumors 68040

    plinden

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    Apr 8, 2004
    #8
    One more idea just occurred to me ... would this affect frame rates in Mac OS X optimized games, like Quake 3, where you would expect a couple hundred fps?
     
  9. jared_kipe macrumors 68030

    jared_kipe

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    #9
    if it had to do with quantum mechanics it would look something like <beam|sync|beam> ;)
     
  10. mkrishnan Moderator emeritus

    mkrishnan

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    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #10
    If Macs start using flux capacitors or get unlicensed portable nuclear power generators strapped to their backs, I'm so getting a Dell. :(

    EDIT: Jared...ROFL...that cracked me up. :D
     
  11. jared_kipe macrumors 68030

    jared_kipe

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    #11
    Thanks, didn't think many people would really dig the Dirac.

    And hell yes, if apple releases a fusion reactor with the next round of powermacs that can power my house. Say hello to my credit card.
     
  12. munkees macrumors 65816

    munkees

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    Sep 3, 2005
    Location:
    Pacific Northwest
    #12
    I noticed on the CPU test with the intel CD 2.0 Ghz it not getting all what it should, is the xbench setup to test dual cores? how would this run on a quad ?
     
  13. plinden thread starter macrumors 68040

    plinden

    Joined:
    Apr 8, 2004
    #13
    What do you get and what do you expect?

    I don't think xBench is very transparent about how it calculates these values, but apparently "baseline", ie. values of 100, is based on a dual G5 @ 2GHz.

    Their calculations can't be just averages of the values they get, otherwise my Disk Test/Random would be 68.11 whereas it's 25.82
     
  14. Heb1228 macrumors 68020

    Heb1228

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    Feb 3, 2004
    Location:
    Virginia Beach, VA
    #14
    Hey! I remember... you know, from Ghostbusters? Don't cross beams or you get the end of the universe or something? Or the stay-puff mashmellow man explodes... one of the two. :D
     
  15. Makosuke macrumors 603

    Joined:
    Aug 15, 2001
    Location:
    The Cool Part of CA, USA
    #15
    Not *maybe* some tearing, on my G5 when I switched from a CRT to an LCD (10.3, which didn't have Beam Sync) there was tearing all over the place. Not that it was a big deal, but every time I drug a window or played a video with decent framerate, it would cause noticible tearing. Most 3D games, of course, enable beam sync, so those were no problem.

    When I upgraded to 10.4, the difference was noticible within the first minute. As far as I'm concerned, systemwide beam sync was the best single new feature in Tiger. According to that tech note it MIGHT cause some speed issues with redraws in certain apps, but I've never seen one--far more likely to just affect synthetic benchmarks like XBench.

    Frankly, now that LCDs are pretty much everywhere, NOT having beam sync systemwide is just plain silly. Fire up Quartz Debug, turn it off, and then drag a large window on any LCD--you'll see what it does immediately.

    EDIT: Woah! I just noticed that every post in this thread but the last was from February... guess this reply wasn't exactly necessary anymore.
     

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