kanex thunderbolt to usb 3 + ethernet adapter.

Discussion in 'iMac' started by jobesucks, Mar 6, 2017.

  1. jobesucks macrumors member

    jobesucks

    Joined:
    Jul 22, 2010
    #1
    Anyone here using a kanex thunderbolt to usb 3 + ethernet adapter.
    I have a mid 2011 iMac with only usb 2 so got the above adapter to add usb3. I've attached a Sammy 850 evo 250Gb to it via a sabrent usb3 to sata adapter (same drive as I've added internally). Running Aja system test and black magic I'm only getting 355MB/s read and write, from external yet get approx 500MB/s from the internal drive. Should there be this much difference between the 2 interfaces, using identical drives?
     
  2. casperes1996 macrumors 65816

    casperes1996

    Joined:
    Jan 26, 2014
    Location:
    Horsens, Denmark
    #2
    Theoretical maximum for USB 3.0 is around 600mbps. Now there's a lot of overhead and whatnot to consider, but you do seem to fall well below that. Then on the other hand (see attached image) this is a test done by MacWorld, and there can be quite a difference between using Thunderbolt/PCIe and USB.
    Does the USB-SATA adapter you use support UASP? macOS does not right now as far as I've been able to gather, but the connectors that support it are also usually just a lot faster than those who don't.
    --- Post Merged, Mar 6, 2017 ---
    Screen Shot 2017-03-07 at 1.16.13 AM.png
     
  3. jobesucks thread starter macrumors member

    jobesucks

    Joined:
    Jul 22, 2010
    #3
    Thanks for reply. Yes adapter does support uasp. Supposed to be optimised for SSD. Thing is it is constant 355MB/s read and write with no fluctuations, as though it's topped out at the adapter(either the sata or the kanex) or it could just be I'm going through 2 adapters.
     
  4. casperes1996 macrumors 65816

    casperes1996

    Joined:
    Jan 26, 2014
    Location:
    Horsens, Denmark
    #4
    Definitely sounds like there's a bottleneck somewhere, though I don't know where it is.
     
  5. Fishrrman macrumors G4

    Joined:
    Feb 20, 2009
    #5
    OP wrote:
    "I'm only getting 355MB/s read and write"

    On a Mac with native USB3, the "max" for an SSD connected via USB3 (with an adapter that supports UASP) is about 432mbps. I have never seen a report of one running faster.

    Considering that you're factoring into the mix ANOTHER "converter" of sorts (the Kanex adapter), I'd say you're getting about all you're going to get... ;)
     
  6. jobesucks thread starter macrumors member

    jobesucks

    Joined:
    Jul 22, 2010
    #6
    Yep figure so, not complaining thats plenty fast enough, just curious as to why such a big difference with the same drive internal.
     

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