Retina 5K Flash Speed Weirdness

Discussion in 'iMac' started by MrGimper, Dec 23, 2014.

  1. MrGimper macrumors 601

    MrGimper

    Joined:
    Sep 22, 2012
    Location:
    Andover, UK
    #1
    I have an iMac Retina 5K i7 with 1TB flash. I also have a 13" 2014 Retina MBP i5 2.8 with 1TB flash.

    Both machines are fitted with the APPLE SSD SM1024F.

    When I run Black Magic on my iMac I get write of ~680 and read of ~720

    When I run it on the MBP I get write of ~900 and read of ~980

    The only difference is that I have FileVault enabled on the MBP, but I would have thought, if anything, that would make the MBP slower

    Why the big difference in speeds?
     
  2. hfg macrumors 68040

    hfg

    Joined:
    Dec 1, 2006
    Location:
    Cedar Rapids, IA. USA
    #2
    The RiMac is only 2 PCI lanes for the SSD, your rMBPro might be 4 lanes (as is the SSD part). They apparently didn't have enough PCI lanes for the iMac to do it right without dropping something else.
     
  3. yjchua95 macrumors 604

    Joined:
    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #3
    The iMac only has 2 PCIe lanes for the SSD, while the rMBP has 4 PCIe lanes available.

    The reason is because the iMac has an extra two USB ports plus an RJ-45 Ethernet port, and these two have taken up two PCIe lanes on its own. So there's only two lanes remaining for the SSD.

    Personally, I wouldn't mind a small sacrifice in speed in return for two more USB ports and the RJ-45 Ethernet port.
     
  4. MrGimper thread starter macrumors 601

    MrGimper

    Joined:
    Sep 22, 2012
    Location:
    Andover, UK
    #4
    Thanks for the replies. At least I know there isn't an issue.
     

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