USB 3.0 drives connecting at USB 2 speed

Discussion in 'iMac' started by jdrouette, Jul 30, 2013.

  1. jdrouette macrumors newbie

    Joined:
    Feb 13, 2013
    #1
    I'm having a hard time getting consistent USB 3.0 speeds from my external USB 3.0 drives and RAID. Most of the time, the ports get configured to "Hi-Speed USB (2) for reasons I can't understand. If I reboot several times, it will eventually connect at the correct speed.

    According to Apple USB 3.0 FAQ, "The first device you plug in will configure the port, so always connect USB 3 capable hubs or devices first."

    I have three USB 3.0 drives connected directly to the 2012 iMac, along with a USB 3.0 hub connecting a few USB 2 devices. When I boot up, I check the System Information and usually see one USB 3.0 bus and 3 USB 2 buses, even though the attached devices should be detected as USB 3.0. How could the buses be configured incorrectly if the only device connected to them is USB 3.0?

    Do each of the 4 USB port correspond to one of the buses? By default, I see that two of the ports are automatically assigned to the Facetime HD camera and Bluetooth host controller, respectively. Is this interfering the the configuration of the ports?

    If a combination of USB 3.0 and 2 devices are connected to the same USB 3.0 hub, how will the port be configured?

    I'm baffled.
     

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  2. old-wiz macrumors G3

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    West Suburban Boston Ma
    #2
    I would expect that the port will go no faster than the slowest device on the hub.
     
  3. Bear macrumors G3

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    Jul 23, 2002
    Location:
    Sol III - Terra
    #3
    On the iMacs I've been able to look up information on and on the 3 different models I've checked out myself, the 4 external USB ports are on 2 different USB controllers. In all the cases, they ports have alternated which controller they're on. If the 2012 iMacs are the same way, the 2 USB ports circled in red on the attached image are on one USB controller and the other 2 ports are on the other controller.

    I suggest you put all the USB 3.0 devices on one controller and all the other USB devices on the other controller and see if that improves the situation.
     

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  4. thedeske, Aug 1, 2013
    Last edited: Aug 1, 2013

    thedeske macrumors 6502a

    Joined:
    Feb 17, 2013
    #4
    Interesting. Mine work "Per Port" - I've had a combo of 2 USB3 externals and 2.0 Printer & Keyboard/Kensington Expert via 2.0 hub plugged (all ports filled) in different port numbers at different times and they show up properly as long as I don't combine 2.0/3.0 in a single port.

    I was concerned when I first set up, so I moved things around to check.

    That said, other drives might work better in the 1/3 2/4 controller setup you suggest. What tricks the system is up for grabs more often than not ;)
     
  5. Bear macrumors G3

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    Jul 23, 2002
    Location:
    Sol III - Terra
    #5
    Looking at the original posters configuration, it might have to do with the USB 3.0 hubs configuring themselves to USB 2.0 hi speed with the detection of the USB 2 devices.
     
  6. jdrouette thread starter macrumors newbie

    Joined:
    Feb 13, 2013
    #6
    Thank for the info, Bear. I think you may be onto something with the alternating ports. I'll need to do more thorough testing, but right now it is working.

    I have two external hubs; one for USB 2 devices, and the other exclusively for 3.0 drives. I thought keeping my 2.0 and 3.0 devices separate might resolve any conflicts. I had never considered trying non-adjacent iMac ports.
     
  7. jav6454 macrumors P6

    jav6454

    Joined:
    Nov 14, 2007
    Location:
    1 Geostationary Tower Plaza
    #7
    Normally the saying goes on to say that in regards to USB your fastest speed will be as fast as your slowest speed.

    So, if you have USB 2.0 devices connected, then, USB 2.0 speeds will be your top speed.
     
  8. jdrouette thread starter macrumors newbie

    Joined:
    Feb 13, 2013
    #8
    For that reason, I've isolated my USB 2.0 devices to a single hub in order to free the other three ports for USB 3.0.

    I'm curious if anyone has managed to successfully configure three out of four ports as USB 3.0, or if only two can work if a single USB 2.0 device is connected. By default, the iMac already has two 2.0 devices built in.
     
  9. thedeske macrumors 6502a

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    Feb 17, 2013
    #9
    Agree
     
  10. h4lp m3 macrumors 6502

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    Jun 29, 2011
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    New Orleans
    #10

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