USB 3.1 for iMAC 2015??

Discussion in 'iMac' started by seekersu, Nov 29, 2015.

  1. seekersu macrumors newbie

    Joined:
    Oct 23, 2015
    #1
    First of all, I know current iMAC has no USB 3.1 (only 4 USB 3.0)

    I recently brought a new external SSD during black Friday, and the speed could reach 550/510 MB/sec (still slower than iMAC internal SSD :)).

    Most current USB 3.0 External Hard Drive Enclosure (Such as Transcend StoreJet 25s3) may not reach the max SSD speed even with the newest Asmedia 1153E SATA3.0 chip, and becomes bottleneck of speed limitation.

    Therefore, I wonder if I connect my external SSD with USB 3.1 External Driver Enclosure through iMAC USB 3.0 port, will there additional speed benefit in comparison with USB 3.0 External Driver Enclosure?
     
  2. hfg macrumors 68040

    hfg

    Joined:
    Dec 1, 2006
    Location:
    Cedar Rapids, IA. USA
    #2

    It won't matter ... the actual speed is still determined by the transfer rates of the enclosed drive, SSD in this case, which is the limiting factor, not the enclosure itself.
     
  3. seekersu thread starter macrumors newbie

    Joined:
    Oct 23, 2015
    #3
    For SSD with speed slower than 400MB/sec, it is ture because most USB 3.0 enclosure could reach around 400 MB/sec. However, some Samsung and Sandisk SSD now is faster than 500MB/sec, and the limiting factor would be the some USB 3.0 enclosure (maybe not all, depend on enclosure quality). Because same SSDs runs slower with USB 3.0 enclosure than with internal SATA. USB 3.1 Gen 2 is faster than USB 3.0, so New SSD could run over 500 MB/sec with USB 3.1 enclosure to USB 3.1 Host (Port on computer). I just wonder with USB 3.0 port on iMAC, will USB 3.1 enclosure still have some advantage?
     
  4. hfg, Nov 29, 2015
    Last edited: Nov 29, 2015

    hfg macrumors 68040

    hfg

    Joined:
    Dec 1, 2006
    Location:
    Cedar Rapids, IA. USA
    #4
    I think your maximum transfer speed is going to be limited by the slowest device in the chain ... be it the USB 3.0 port on your computer, the disk drive itself, or the USB 3.1 port on the external enclosure. However, other than running specific benchmark tests, I doubt you will ever notice any speed differences in actual use yet alone even see speeds approaching the published spec maximums.

    Also, don't forget the TRIM issues with SSDs on USB 3.0 interfaces vs. Thunderbolt.
     
  5. kohlson macrumors 6502a

    Joined:
    Apr 23, 2010
    #5
    The USB3 spec is around 5Gbps, a theoretical number, or 500MBps. So while you can connect faster drives in various configurations to approach this number, it cannot be reached or exceeded. I suspect it's one reason Apple went to PCI-based storage (and by extension, TB). The Black Magic test on my 2014 rMBP exceeds 800MBps, both read and write. And if I remember correctly, the 2015's are even better.
     

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