How does USB 3 work on the rMBP 15*

Discussion in 'MacBook Pro' started by hajime, Jan 21, 2013.

  1. hajime macrumors 68030

    Joined:
    Jul 23, 2007
    #1
    Hello, on the rMBP 15", there are two USB 3.0 ports. I just bought a USB 3.0 hub. How does connection of one USB 2.0 device (either directly to the laptop or via the USB 3.0 hub) affects the connection speed of the rest of the devices? In the past, when you connected a USB 2.0 device to a USB 3.0 port, the USB communication between the computer and its devices dropped from USB 3.0 to USB 2.0.
     
  2. kitkat99333 macrumors newbie

    Joined:
    Jan 21, 2013
    #2
    When you plug a USB 2 device directly into a USB-3 port it will operate at USB-2. This is because a USB-3 port actually has two lines in it if you will, a USB-2 Line and a USB-3 line.

    When you plug a USB-3 Hub in it will act as a hub for both the USB-3 line and the USB2- Line. So if you had a 4 port USB-3 hub with 2 USB-2 devices and 2 USB-3 devices, the 2 USB-2 will share a 450 mbps line( a USB-2 line) between them and the 2 USB-3 devices will share a 5gbps line ( a USB-3line).

    So the USB-2 devices and USB-3 devices in simple terms operate on different lines back to the USB controller on the motherboard.
     
  3. hajime thread starter macrumors 68030

    Joined:
    Jul 23, 2007
    #3
    Thanks. So, plugging a few USB-2 devices on the rMBP or USB-3 hub won't slow down the connections of other USB-3 devices.

    Do all the usb3 hub act the way you described? Or is it up to the manufacturers?
     

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