Question USB ports not enough power

Jun 1, 2022
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My back panel USB ports don't give enough output power to support external disk (2.5"). But the front does. Back port give around 4.0V, front 5.0V.
USB ports are 3.1, external disk is 3.0. Ordinary USB is working fine without problems, maybe quickly become hot. Any ideas what could be the problem and how to solve this?
 
Jun 1, 2022
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Motherboard: MSI B450 TOMAHAWK
BIOS: AMI1.H7
Case: Cooler Master MasterBox E500L
External disk: WD My Passport and WD Elements
 

Paperdoc

Polypheme
Ambassador
Maybe you're trying the wrong ports. There are BOTH USB2 and USB 3.2 Gen1 ports on the back panel in the older Type A form. The two ports below the PS/2 (keyboard) socket are USB 2, able to provide power at 5 VDC at up to 0.5 A each. These should have black inserts. The two above the HDMI socket are USB 3.2 Gen 1 in Type A, and each should have a blue insert. The two ports below the LAN socket are both USB 3.2 Gen2 sockets - one Type A, one Type C.

What you describe is typical of trying to use a USB2 socket / port with an external "laptop Hard Drive". This drive type now prdominates, but their design uses low-performance and hence low-power-yse drives so they can just work on the ISB3.2 power lomit of 5 VDC st 0.9 But they can NOT work on a USB2 socket, even though some of them claim "USB2 compatability". What that really means is that they will work IF you arrange somehow to provide them with the USB3-level power source of 0.9 A.

By the way, the labels have changed but many items were made and labelled before the change, so it's confusing. There is older USB2 stuff still in use. ALL of the new stuff now is called USB 3.2 with a "Genn " following. The differences in the Gen's are mostly oin the max communication speed the link can do. Gen1 can do up to 5 Gb/s, Gen2 can do up to 10, and Gen 2x2 can do up to 20 Gb/s. Those are max speeeds for the communication subsytems, and they are deliberately made too high so that they will NOT become limits on the performance of the other parts (like a HDD, or an SSD) of the attached unit. VERY few devices today can achieve 10 GB/s actual data thoughput, and virtully none get to 20. But those things may come. Irrespective of the speed rating (Gen number) of a connected USB 3 device, they ALL should work with any of these host computer ports, limited by the device speed, not usually by the port speed.
 

Paperdoc

Polypheme
Ambassador
So you are using the right rear ports. The fact that the unit does show up in Device Manager only means that the communication subsystem CAN find the external drive properly. But it does NOT guarantee the drive will actually work. For that situation, the failure normally happens when you try to USE the drive because spinning the disk for reads and writes is what requires the most power.
 

Paperdoc

Polypheme
Ambassador
I just noticed something. WD sells three types of external hard drives. The WD My Passport line comes only as the small "Laptop Hard Drive" for use with a USB 3.2 Gen1 port, and that comes with NO accessory power "brick", and NO port on the drive unit for plugging one in.

The WD Elements PORTABLE hard drive line is similar.

The WD Elements DESKTOP Hard Drive line is larger units for use with USB 3.2 Gen1 ports, BUT these units require more power and DO come with an accessory power "brick" and DO have a socket on the case where you plug that in.

So which type of WD Elements unit do you have? Can you tell us a model number? Is it ONLY that unit that fails to work? Or, do BOTH WD external hard drives fail for you?
 
Jun 27, 2022
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My back panel USB ports don't give enough output power to support external disk (2.5"). But the front does. Back port give around 4.0V, front 5.0V.
USB ports are 3.1, external disk is 3.0. Ordinary USB is working fine without problems, maybe quickly become hot. Any ideas what could be the problem and how to solve this?
It seems that we have a similar issue, all my ports are fine except these 2 ports on the pic below, they don't deliver enough power for my keyboard or my external hdd. I've tried to update bios, use another PSU or run Linux to avoid driver issues, it doesn't work.
I have a B450 gaming plus max bios 7B86vHF (H.F1)
 

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