mini usb 3 and perhipherals/ input devices

Discussion in 'Mac mini' started by macmesser, Jan 6, 2016.

  1. macmesser macrumors 6502a

    Joined:
    Aug 13, 2012
    Location:
    Long Island, NY USA
    #1
    I noticed that on 2012 i7 there is a bluetooth controller on the USB bus, and also that both usb 3 drives and bluetooth can impact wifi performance to a variable degree. I apparently had a bad card which made wifi speed degrade to an unusable point, which I found could be worked around by removing USB and bluetooth devices and switching to wired mouse and keyboard. With the new wifi card this has been eliminated but I still see an effect on wifi speed when USB devices are used and/or bluetooth is enabled. Could be connection speed variation or Cablevision throttling repeated speed tests. (I use Speakeasy and Comcast for test.) At any rate, the whole thing has got me wondering about the USB bus in general and as it relates to bluetooth. Specifically, I'm wondering if the bus reverts to USB 2 when a wired input device is used.
     
  2. treekram macrumors 6502a

    Joined:
    Nov 9, 2015
    Location:
    Honolulu HI
    #2
    I can only address the bus issue.

    On my 2012 i7 Mini, when I do the system report, what I think I see are 3 USB buses. There is no bus # information but that's what I think is the case. Somewhere along the line, specific bus information got lost because on my 2009 Mini running Snow Leopard, it showed the bus # so I would know if a bus was being shared. In any case, if my assumptions are correct about the 2012 Mini, one bus is used by Bluetooth, one for USB 2 and one for USB3. I have a USB hub with both USB2 devices (Keyboard and mouse connected to the keyboard) and USB3 disks which are plugged in as needed. I also have 2 USB3 external disks connected directly to the Mini. But System Report shows them being separated into their respective buses (USB2 devices to the USB2 bus, USB3 devices to the USB3 bus), with Bluetooth having it's own bus.

    Assuming I'm correct, USB3 devices have their own bus and should not be affected by USB2 devices. That's what I notice. Besides the keyboard, I have USB2 external disks and flash drives and have not noticed performance degradation on the USB3 devices when the USB2 devices are attached. On my 2014 Mini, I think USB2, USB3 and Bluetooth all share the same bus and I have a USB2 keyboard and mouse and have not noticed USB3 performance issues there.
     
  3. macmesser thread starter macrumors 6502a

    Joined:
    Aug 13, 2012
    Location:
    Long Island, NY USA
    #3
    Thanks for sharing. Your assumption seems reasonable. On mine the infrared controller is on one of the buses as well. It is interesting that seemingly the different usb versions can coexist but remain transparent to one another. I always thought the slowest device brought everything else down to its speed.
     
  4. Celerondon macrumors 6502a

    Celerondon

    Joined:
    Oct 17, 2013
    Location:
    Southern Cal
    #4
    Ugh! I hope not. This would be a dismal world if USB 3.0 reverted to USB 2.0 any time that someone plugged in a legacy device. :oops:

    Backwards compatibility could take on a sinister meaning in such a world. Drastic measures like public bonfires and component crushing might become popular to weed out the speed killing old stuff. ;)
     
  5. macmesser thread starter macrumors 6502a

    Joined:
    Aug 13, 2012
    Location:
    Long Island, NY USA
    #5
    LOL! And time in The Institute for Regressive Tendencies for those harboring any old components in their basements.
     

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