5 Replies Latest reply: Jul 29, 2014 8:25 AM by pinknoize
DigitalDuderino Level 1 Level 1

I have the late 2012 27 inch iMac with four USB 3.0 ports


My question is, can each of these ports run at full USB 3.0 bandwidth INDEPENDENTLY of each other?


I want to plug a device such as Kensington's SD3500v Docking Station in to one of my USB 3.0 ports and want to make sure that won't adversely affect the speed/bandwidth capability of the other free USB 3.0 ports on the back of the iMac.


Thank you for any concrete facts anyone can provide. I have been unable to find the answer on my own.


I'll be going into an Apple store tomorrow to ask a genius if I can't find the answer out online.

iMac, OS X Mountain Lion (10.8.4), 24 GB RAM
  • Dr.Mac. Level 3 Level 3

    Each USB 3.0 port run at full bandwidth with a transmission speed of up to 5 Gbit/s.  Instead of one-way communication, USB 3.0 uses two unidirectional data paths: one to receive data and the other to transmit.




  • DigitalDuderino Level 1 Level 1

    Thank you! Can you point me to the Apple doc where you found that information?


    Much appreciated.

  • Dr.Mac. Level 3 Level 3

    Use your iMac System Information utility. 

    1. From the Apple  menu, choose About this Mac.
    2. Click More Info.
    3. Click System Report.
    4. In the Hardware section of the System Report, click USB.
    5. You will see the USB 3 section.
      All your USB 3 devices will appear in the "USB 3.0 SuperSpeed" section. 
      Clicking the disclosure triangle will allow you to see more details.

      Ref: http://support.apple.com/kb/HT5172

      All the USB 3 hubs and USB 3 devices that conform to what is referred to as the  "2008 version 1 USB 3.0 specification" are supported. The first device you plug in will configure the port, so always connect USB 3 capable hubs and/or devices first.

  • Rudegar Level 7 Level 7

    what needs the speed?

    you'd be pretty hard pressed to find something you can connect where the usb3 even at 1/2 bandwidth would be the bottleneck

    maybe a ssd ext disc

  • pinknoize Level 1 Level 1

    I would also like to know the answer to this specific question.  Did anybody find concrete documentation regarding this specification?


    Our team wanted to know if each USB 3.0 port had it's own bus able to run the theoretical 5 Gbps speed or is the theoretical speed shared between all of the ports.  I ran across a post on Mac Performance Guide that spoke about the ports on the new Mac Pro (2013) that said the USB 3.0 ports share one single bus.  In contrast, it states that the Retina Macbook Pros run each USB 3.0 port on independent busses, thus resulting in better performance.


    So the question still stands, how does the 2012 iMac handle USB 3.0 speeds?  Please provide credible documentation if you have the answer.


    Thanks for any help you can provide!