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dlbmacfan

macrumors regular
Original poster
Jul 20, 2011
177
71
I have a new MBA that supports USB 3.0, and I just purchased a USB 3.0 external drive. The drive works great when I plug it into the USB port next to the MagSafe 2 port, but it's not recognized when I plug it into the USB port next to the Thunderbolt port. The power light does light up on the drive, but Finder can't see the drive. Any ideas on why this might be happening? Is there a difference between the two USB ports?
 
Not that I can see. I plugged in a USB 3.0 Seagate drive (1.5TB) and the USB port on the right side powers it fine.
 
There shouldn't be a difference. Can you see the drive in disk utility?

I plug my MyPassport USB 3 drive into both sides fine.
 
I have one possible but unlikely reason. Typically the USB port(s) closest to the processor on a computer will provide a bit more power/speed than USB port(s) that are further. So if your processor is closer to the left side of your laptop, the left side port(s) will provide a bit more power. The difference shouldn't be big however if you're using a USB drive that is powered via USB, it could be that the slight difference in power is just enough to not fully recognize your drive on one side. It may provide just enough power to turn it on but not enough to mount it and make it available for transfer.
 
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