5k imac USB3 port faster than Mac Pro, is it normal?

Discussion in 'Mac Pro' started by Amethyst, Jul 27, 2016.

  1. Amethyst macrumors 6502a

    Joined:
    Aug 8, 2006
    #1
    i have test my mac pro 2013 & imac 5K usb3 external disk performance using same drive (Transcend Storjet 25s3+intel 530 ssd peak (500/550mb)), and i found that mac pro is somewhat slower than iMac as shown in attached image.

    is it normal?
     

    Attached Files:

  2. kennyman macrumors 6502

    Joined:
    May 4, 2011
    Location:
    US
    #2
    Checked the test file size, noticed:

    nMP - 512 MB
    iMac - 1 GB

    I would suggest to run the test again with the same file size.
     
  3. filmak macrumors 65816

    Joined:
    Jun 21, 2012
    Location:
    between earth and heaven
    #3
    nice find, file size certainly makes a difference.
     
  4. Amethyst thread starter macrumors 6502a

    Joined:
    Aug 8, 2006
    #4
    just change file size to 1GB, nothing change.
     

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  5. chrfr macrumors 604

    Joined:
    Jul 11, 2009
    #5
    The 2013 Mac Pro has hardware limitations on USB 3 performance. It's not surprising that the iMac is faster as with that computer, USB 3.0 is integrated into the chipset.
    http://macperformanceguide.com/MacPro2013-USB3-performance-limitations.html
    http://www.anandtech.com/show/7603/mac-pro-review-late-2013/8
     
  6. Joe The Dragon macrumors 6502a

    Joined:
    Jul 26, 2006
    #6
    The mac pro is also at the limits of PCI-E moving usb 3 to the chipset will not help that much as the chipset DMI link is only pci-e 2.0 or 3.0 X4.
     
  7. ActionableMango macrumors G3

    ActionableMango

    Joined:
    Sep 21, 2010
    #7
    I assume so. I've seen similar results with my 2010 MP and a 2012 Mini. The Mini is a little bit faster.

    And I'm even seeing the same difference when using rotational hard drives. There's certainly no bottleneck slower than the rotational hard drive itself, so why is there a speed difference between the two computers? I assume there's something in the Mini's chipset or the CPU itself that lets it handle data transfer more efficiently.
     
  8. mmomega macrumors demi-god

    mmomega

    Joined:
    Dec 30, 2009
    Location:
    DFW, TX
    #8
    Interesting though.
    I'd like to test this myself across a few different Macs of various years.
     
  9. ColdCase macrumors 68030

    Joined:
    Feb 10, 2008
    Location:
    NH
    #9
    Latency and HD cache affects USB protocol in unexpected ways. So a rotational drive could performs differently from one host USB implementation to another. Its more than the number of bits than can be pushed through the pipe as the drive may write and acknowledge which can have some variations.
     

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