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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > USB port power

USB port power
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imdipped
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Apr 10, 2015, 09:21 PM
 
on macbook pro 3,1 which usb port has the most power?
     
Mike Wuerthele
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Apr 11, 2015, 09:51 AM
 
If its functioning normally, they all have the same.
     
imdipped  (op)
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Apr 12, 2015, 08:27 PM
 
The sites that describe my late (June 2007) MBP say that only one of the usb ports has full power. MBP's that have both ports on the same side, the one in the front gets full power. My MBP has one on each side but nowhere can I find where it is stated which one gets the full power.
     
reader50
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Apr 12, 2015, 08:49 PM
 
I think this is your model.
Unlike earlier models, where every USB port could provide 500 mA of power, only a single high-powered device can be attached to the USB ports, and software will enablejust one of its downstream ports to supply 500 mA of power. If a second high-powered device is attached, it will behave like a normal bus-powered hub and only provide 100 mA per downstream port.
Based on the description, it isn't a specific port. Both ports offer 500 mA, but only to the first taker. When you plug in a higher-power USB device, the other port will be limited to 100 mA. Until you unplug the high-powered device, at which point both ports will offer higher power again.
     
imdipped  (op)
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Apr 13, 2015, 12:13 AM
 
Thank you. I understand.
     
Spheric Harlot
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Apr 13, 2015, 06:22 AM
 
On my early 2011 13" MacBook Pro, I have had situations where USB devices would not work correctly when powered from the rear USB port, but be fine on the forward one.
     
donaldkepler
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May 15, 2015, 04:40 AM
 
USB-C port gives the maximum power in MacBook pro 3.1.
     
   
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