Subjective speed of i7 iMac

Discussion in 'iMac' started by smirk, Jun 28, 2011.

  1. smirk macrumors 6502a

    smirk

    Joined:
    Jul 18, 2002
    Location:
    Orange County, CA
    #1
    Hey guys, I just got a new 2011 27" i7 iMac. The display is beautiful, and I'm sure it is plenty fast and will last for years, but right now in my limited use it doesn't seem as fast I was expecting. I was wondering if there are certain apps that maybe don't take advantage of the Sandy Bridge speed or something.

    This computer replaces my 2006 iMac Core Duo, so I was expecting the new iMac to be something like 4 times faster (based on benchmarks), but so far I haven't noticed that kind of speed increase. iMovie still takes about 30 seconds to load in video clips, and iPhoto's "rebuild database" process took over 1/2 hour to run, maybe even closer to an hour. While it was running, everything slowed way, way down, even though only one core was saturated, so I'm wondering if the hard drive is the bottleneck.

    Anyway, for those of you who bought a new Mac, were you satisfied with the speed? Did certain types of operations "show off" the Mac's speed more than others? In summary, I guess I thought it would be "blazing" but instead it's merely " pretty fast".

    Thanks for your thoughts.
     
  2. mrfoof82 macrumors 6502a

    Joined:
    May 26, 2010
    Location:
    Lawton, OK
    #2
    Loading in video clips is I/O bound, not CPU-bound.
    Rebuilding an iPhoto database is I/O bound, not CPU-bound.

    The way to truly see the performance difference is to replace the slowest part that is bottlenecking your task -- in your examples this is not the CPU, it's the storage device (in your case, the hard disk). The difference would be far more pronounced with an SSD-equipped iMac instead of a hard-disk equipped iMac.

    The reason being is not only does the SSD have a higher sustained transfer rate than a hard disk (which would mostly affect the first test), but also can perform 70-100x more I/O operations per second (which would much more drastically affect the second test).
     
  3. smirk thread starter macrumors 6502a

    smirk

    Joined:
    Jul 18, 2002
    Location:
    Orange County, CA
    #3
    Yeah, you're right of course. I figured it was I/O bound, because Terminal shouldn't take 5 bounces to launch. Still, I guess I figured that five years would bring faster hard drives and, I don't know, better task scheduling. The drive sounded like it was severely fragmented -- I do know all about OS X's built-in defragmenting methods, but that's how it sounded, grinding away like crazy while processing the photos.

    I guess the true power will manifest when I try actually using iMovie while running Handbrake and Folding@home at the same time. :)

    Thanks for your comment.
     
  4. mrfoof82 macrumors 6502a

    Joined:
    May 26, 2010
    Location:
    Lawton, OK
    #4
    Hard drive performance is limited by how fast the platters spin, how fast the arm can move the head, and the areal density of the disk itself.

    7200 rpm is no faster than 7200rpm. The servos aren't faster. So any improvement will be due to areal density. This will help mostly for sustained transfer rate for contiguous files. Non-contiguous files that require head movement? Little to no improvement.

    The only way to improve are faster drives, more drives, or solid state. In terms of bang for the buck (for performance, not total aggregate storage area), solid state is the best option by a huge margin. In a data center, 1 SSD has I/Ops throughput that utterly humiliates an entire DAS (14 disks) of 15krpm SAS disks.
     

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