Only two USB 3 busses

Discussion in 'Mac mini' started by woodbine, Nov 30, 2012.

  1. macrumors regular

    Aug 8, 2010
    Bath, UK
    I had a look at system report for my new MacMini 2012 and it says only two USB 3 ports and two USB 2 ports.
    Is this correct?
  2. macrumors G4


    Sep 7, 2006
    In the velcro closure of America's Hat
    That is correct. Ivy Bridge CPUs have two USB 3 bus controllers built in and there is no other onboard bus controller on the logic board.
  3. macrumors 68000


    Sep 16, 2008
    So 2 ports per bus then? You make it sound like only 2 of the 4 ports are at USB3 speed. Per Apple's site, all 4 ports are USB3.
  4. WLS
    macrumors 6502a

    Jul 10, 2008
    Is one bus controller for internal devices and the other for external? E.G are all 4 of the USB rear ports on the same bus?
  5. macrumors 68040

    Dec 17, 2009
    This is the standard setup for almost all computers. Any computer you buy, generally does not have a 1:1 BUS to port ratio, usually it is 1:2 bus to port (sometimes the ratio is even worse). Some laptops that have very few USB ports will have a 1:1 (if the only have 2), but even a friend's Fujitsu 12" laptop I used the other day had 3 USB ports and it was split with 1:1 on one USB port and 1:2 with the other two.
  6. macrumors 6502

    Nov 2, 2007
    So is there a way to know which ports are USB3? (via the system profiler porbably, correct?)

    This is sad, I thought it had four USB3 ports :(
  7. macrumors 68040

    Dec 17, 2009
    You misunderstand, they are ALL USB3, just that two will share USB3 bandwidth so if you plugged two high bandwidth items into two USB3 ports that share the same BUS, they might experience a slow down. Granted USB3 is faster than any mechanical hard drive can output (or two for that matter), so it would have to be something like hooking SSD's via a USB3 port that you might see this issue.

    EDIT: Think of it like 2 port USB hubs.
  8. macrumors 65816

    Jul 7, 2008
    It does. All the USB ports on the rear are 3.0.
  9. macrumors 603


    Apr 13, 2010
    the mini is auto detect. plug in 4 usb3 devices restart the machine and all 4 ports will show usb3. plug in all 4 usb2 devices the mini will show 4 usb2. any combo it will show.

    Now as to the ability to run 4 usb3 devices at full speed at the same time most likely it can't do it. you could try to test it but not sure if it can be done that easy.
  10. rkahl, Nov 30, 2012
    Last edited: Nov 30, 2012

    macrumors 65816

    Jul 29, 2010
    What's the difference between USB 3 Hi-Speed and USB 3 SuperSpeed?
  11. macrumors 65816

    Jul 7, 2008
    There is no USB 3 hi-speed. Any reference to hi-speed is USB 2.
  12. macrumors 65816

    Jul 29, 2010
    My 2012 Mac Mini system report says that I have a USB 3.0 Hi-Speed Bus and a USB 3.0 SuperSpeed Bus. What's the difference?
  13. macrumors 65816

    Jul 7, 2008
    It's telling you that you have a USB 2 bus...I think.
  14. macrumors 65816

    Jul 29, 2010
    Sorry to sound dumb, but how do you know if you are plugging your external hard drive into a USB 2 or a USB 3 port?
  15. macrumors 65816

    Jul 7, 2008
    As far as I know, all the rear ports are USB 3. If you have a USB 2 device hooked up though, it might read as something lower than USB 3 super speed.
  16. macrumors 6502

    Nov 2, 2007
    Thanks for the explanation.

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