I bought a flash recently, In the warranty card there was a caution saying "Always use USB ports on the back of the case" . Is there any difference between front and back ports? They are all connected to the MoBo the same way providing the same voltage, functionality etc?

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    +1. I'd like to know as well!
    – agirish
    Commented Dec 27, 2012 at 18:06
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    a simple google search gave me this info - yes there is a difference! Mainly to to do with power. Hence it affects performance. The back ports have more power capability
    – agirish
    Commented Dec 27, 2012 at 18:10
  • and you are less likely to bump the computer and disconnect the plug when its on the back. for stuff like flashing a phone's rom over usb, it is always recommended you use back ports, both for power and stability. Commented Dec 2, 2013 at 13:01

8 Answers 8


I have had motherboards in the past that provided usb 1 on the headers (which connected to the front of the case), and provided usb 2 to the ones mounted/attached to the back of the board itself (aka the back ports).

This is purely a design choice made by the board designer(s).

With respect to your flash-memory stick, the manufacturer of that device is gambling on the idea that the ports on the back are going to be the highest supported standard at the time of the board's manufacture. Since they did not design your motherboard, they have no way of knowing for sure.

They need to make a statement for the people most likely to need the statement made. More technically minded individuals will probably know that the generalization made int he manual is too narrow. For the less technical, if they follow what is written, they are more likely to not have problems with the device.

Oversimplification is a common teaching tool, and one of the reasons that technical fields must re-teach certain subject at the college level to correct these errors or over-specifications in high school level classes.

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    "With respect to your flash-memory stick", I liked that ! So, You believe it's an "Oversimplification" & presumption ?
    – Sam
    Commented Dec 27, 2012 at 18:23
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    Similar - superuser.com/questions/127796/…. I came to the same conclusion, that it's up to to how the motherboard maker wants it to be. Only other possiblity I can think of is that the rear are built on the board, but the front require a cable, which could possibly get connected wrong and either not work right or cause damage.
    – Bratch
    Commented Dec 27, 2012 at 18:25
  • @sam: yes, I think so.
    – horatio
    Commented Dec 27, 2012 at 18:28
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    The front ports could damage the card if the the +5V and -5V wires are inverted.
    – Fábio
    Commented Dec 27, 2012 at 19:11
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    @sotn I think these days it's more rare, but the early USB connectors were a bunch of individual wires that you must make sure to connect properly.
    – Fábio
    Commented Feb 22, 2021 at 15:34

I have been surprised to find how little information there is out there about USB 3.0 ports, how they are powered, and the typical problems we all run into with them.

I have spent some time digging around the interweb and found a few tid bits of interest, as well as my own experiences:

So to do with the front panel headers on motherboards and adapter cards for USB 3.0 - the standard output for these connectors is limited to 500 mA, which paired with the front headers themselves being connected with long, high gauge, poorly shielded, and relatively poorly made cables makes a storm of bad communication and underpowered front ports, especially when trying to use fast devices like USB sticks and USB-powered external hard drives!

I myself have encountered poor write speeds on my USB sticks in the front USB 3.0 ports, and they periodically drop out, as well as serious drop outs or not even being able to read or power external HDDs that are powered through the USB cable. These problems never occur when I'm using the back ports directly off my mobo or adapter card, and going back to the power issue, this is because the USB ports on the mobo provide 900+ mA of power, and the front header ports are only given 500 mA of power (found this out through tech support for one of my cases).

Now all this being said, there are other factors at play as well. One big one is poorly shielded internal front panel cables which use high gauge wire and the length of the wire alone creates resistance which slows device communication down. This problem does not exist on the mobo ports because they are directly connected to the controller with no China made cables in the way to interfere.

Another issue commonly run into is drivers. If you have poor drivers or windows drivers they usually always slow things down or lead to the ports not working at all, so make sure if at all possible that you have the correct drivers for your system.

Lastly I have read of several instances where computer cases have had defective front panel USB 3.0 cables and/or ports/connectors leading to a plethora of issues such as drop outs, no communication and poor communication with devices leading to data corruption.

So in conclusion my advice would be to make sure your drivers are up to date and correct, and to really just avoid using the front USB 3.0 ports if at all possible, the rear ones are significantly more reliable and stable.

Good day everyone!


There is a difference in power level only, as some device needs high power (500 mA instead of 100) to charge or function. Where the port is located does not matter. Not sure what it means really in your warranty card. You might ask the manufacturer. Many of my devices such as netbooks and laptops have ports on the sides, neither back nor front, actually.

  • Which ports provide 500mA & which ports 100 mA? And why is that? isn't the way they connect to MoBo the same?
    – Sam
    Commented Dec 27, 2012 at 18:18
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    you should check your computer manual or your OS facilities such as control panel/device manager or something similar on your OS. For instance, my windows 7 pc device manager tells me that my usb root hub is 500 mA. My old laptop however only has 100mA usb ports.
    – johnshen64
    Commented Dec 27, 2012 at 18:29

The main difference is the way the signal travels inside your computer.

The back ports are (usually) directly connected to your motherboard. Their on-board connection to the actual USB controller is designed to resist (EM) interference, as required by the FCC. So is the external connector.

The front ports are not directly connected to your motherboard. Instead, there is a cable inside the computer case that is connected to a regular pin header on your motherboard. The length of this cable and the fact that it’s a pin header connection make it more susceptible to (EM) interference. The internal USB cable may even be unshielded.

This additional cable also means there’s additional resistance, reducing maximum voltage and thus power. Some devices (like 2.5″ hard disks) that can barely run on a single USB may fail in this environemnt.

tl;dr: Front ports are more susceptible to power and signal quality issues.

  • Surprisingly this is the only useful answer. Last year I have bought a beautiful and otherwise nicely built PC case. But I have always experienced problems with the USB2 ports on the front, and yesterday a USB stick put to the USB3 front port always had ~10 checksum errors with a 10GB file (on the back ports and on a laptop there were no problems at all, so it's not damaged flash memory). The cables from the front panel had no ferrite chokes whatsoever, and the USB2 cable even was a f*cking unshielded ribbon cable. I put some chokes on them and now everything's fine.
    – oliver
    Commented Feb 17, 2020 at 10:28

Actually by "Always use USB ports on the back of the case" they probably mean: don't use extension cables or hubs but use a "real" usb port.


It depends entirely on the motherboard. With my motherboard (Sabertooth X58) there are two rear USB 3.0 ports and that's it. The rest of the rear USB and the front USB are 2.0. Older boards had a similar dichotomy regarding 2.0/1.0. Some modern boards have less 3.0 ports to reduce costs (but usually use 3.0 up front). However, there is no reason I am aware of for front USB to be "dangerous" to a device, just sub-optimal for those boards with no front 3.0.


well there are no performance issues. the front ports are part of the cabinet and the back ports are part of motherboard.(but the front ports are also attached to the motherboard using wires.) Back ports are used to provide more sockets for connecting peripherals on back. and the front one are for easily and quickly removable peripherals.As the back ports are soldered to MB it is better to use them less frequently. but its up to user.


Yes, there are differences between them. The back USB ports are controlled by GMCH (graphics memory controller hub), which is directly operated by rich (south bridge) whereas the front ports are controlled by I/O controller. GMCH controlled back USB ports give more power and directly connect the device to the motherboard unlike the front, which work on system IRQ.

  • This would be the design choice for some but not all computers from a decade ago. South bridges went out of fashion quite a while ago.
    – MSalters
    Commented Jul 29, 2014 at 14:44

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