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USB 3.0 extremely slow

I have a MacBook Pro with USB 3.0. If I plug a Western Digital My Book drive into it, it's crawlingly slow (100kbps). If I plug a USB 2.0 drive into it, it's as fast as the disk. If I plug the USB 3.0 drive into my older Mac Mini (USB 2.0) it's also as fast as the drive. Why is USB 3.0 so much slower than 2.0?

MacBook Pro with Retina display, OS X Mavericks (10.9)

Posted on Feb 24, 2014 12:37 PM

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3 replies

Feb 25, 2014 6:46 AM in response to moosehooey

Keep in mind that the very first device you connect will determine the default speed for the entire USB bus. So, if you boot up the MBP, log in, and plug in a USB2 device, then the bus will never operate faster than USB2. You would then need to reboot the computer, and first connect the USB3 device to ensure the bus steps up to USB3 speeds for USB3 devices.


Also, make sure you are using a USB3 compatible cable with any USB3 devices to get max. transfer speeds.


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

USB 3.0 extremely slow

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