The following advice is based on years of experience. It is provided as a free service to our customers and visitors. However, Directron.com is not responsible for any damage as a result of following any of this advice. You are welcome to distribute these tips free to your friends and associates as long as it's not for commercial purposes. You are permitted and encouraged to create links to this page from your own web site.
Front mounted USB is a fairly old concept, but it has been one that has been tricky for most people to hook up. In order to have front mounted USB you must have 3 things.
- A case with USB ports in the front of it.
- A motherboard that supports front USB (usually)
- Appropriate wiring between the USB port and the motherboard
A case can support front USB in two ways: via a pass thru connection, or via a port to header connection. The former, pass thru connection, is compatible with all motherboards that have USB ports.
Pass thru front USB
Pass thru front USB works by having the ports on the front of the case connect to either a standard USB cable, or a fairly small rounded cable. The cable goes from the front of the case to a special slot cover with either a hole (for the standard USB cable) or a special connector for the rounded cable. If the pass thru USB had a standard cable, then you would simply plug the standard cable into one of your back USB ports. If it had a rounded cable, then you have a secondary attachment with something that looks like an old style SCSI connector. The attachment plugs into both the slot cover, and the back USB ports. The draw back of pass thru front USB is that you lose the ports in the back.
Many 3rd party devices that add front USB to a system use the pass thru system. A good example is this now discontinued Front IO panel
Front USB via a Port to Header connection
In order to hook up a Port to Header connection you have to make sure that the wires from your port will connect to your motherboard's header. To do this you need to know what header you have, and what type of connector you have on the wires. You'll find information on both below.
Almost all motherboards these days have a USB header. Due to size and cost restraints many motherboards only have 2 USB ports on their back panel, but often they can actually support more then 2 USB ports. They will typically support additional ports via the use of a USB header. A USB header is either a single or double row of header pins on the motherboard that can be used to add additional USB ports to a computer via the use of an appropriate set of header connectors, wires, and a USB port. Each pin on the header corresponds to a wire inside a USB cable. These pins must be clearly marked so that you can hook them up to the wiring correctly. There are 2 common layouts for a USB header.
Intel Standard USB header Layout: (used by over 90% of motherboards)
Gigabyte Style USB header Layout: (used most commonly on Gigabyte brand motherboards)
Now that we know the types of headers we have to take a moment to understand the USB wiring.
Understanding the wires
First off: All USB cables have 5 wires. 4 of these wires are actively used. Here's a reference from the official USB standard.
On a front mounted USB port you'll have either the first 4 wires connected to properly colored wires (red for power, white/orange d-, green/yellow d+, black for ground) or all five wires attached to the port (same as the former, but one extra black wire). Now where it gets tricky is how to attach each of those wires to corresponding pins on the motherboard.
The wires are "tailed" (attached to a header connector) using any one of a number of different types of connectors. Below you'll find a list of the common ones.
Common USB case header connectors
4 joined pins + 1 extra ground.
Compatibility: Compatible with both header arrangements because of the extra ground. May not work with some odd arrangementsTo hook up carefully match each pin. For the Intel hookup you'll have the extra ground wire not attached to anything. For the Gigabyte hookup you'll have the extra ground hooked to ground pin on the motherboard, and the standard ground jumper will be over the missing pin on the header.
All pins separated
Compatibility: Compatible with every header. If all the pins are separated the only real issue is lining up the pins with the appropriate places on your header. It should be compatible with all headers. Just make sure you read the writing on each individual connector.Please check the troubleshooting info at the end of the article for important information on this configuration
Power and Ground separate, d-, d+ joined Lian-Li style
Compatibility: Compatible with all common headers. This sort of arrangement is common to almost all Lian-Li cases. Make sure that you get the wires connected to your header in the proper order. If you find that the port does not function the most common cause is accidental reverse of the d-,d+. Try switching it.
All pins joined Intel style easy connector
Compatibility: Compatible with Intel standard only. This type of connector is specifically design to mate with the Intel type header that I described earlier in this guide. One pin is blocked so that it is impossible to install improperly.
All pins joined Gigabyte style easy connector
Compatibility: Compatible only with boards with a Gigabyte style header. Most Gigabyte motherboards come with a dongle cable that turns your front USB into additional back USB ports via a empty slot on the back of your case. These dongle cables use the Gigabyte style easy connector. You'll never see these sorts of connectors on a case, unless it's for a custom Gigabyte only solution. This type of connector can not be installed backwards due to the keying of the pins.
Making the Connection
Once you know what type of header you have, and what type of connector you have on the wiring, you need to connect the two of them. In order to do this, you must first figure out what pin goes with what part of the connector. To do this, you should first consult your motherboard manual. Below you'll find an excerpt from a fairly recent motherboard manual for the Asus A7M266 motherboard. It's typical of a motherboard manual for a board using the Intel standard USB header.
The first thing you'll probably notice is that the wiring from your case and the names of the pins might not quite match up name wise. This is a common problem. Motherboard makers and case makers really haven't decided on what to call each pin. Here's a rough list of names.
Power may be called: P, VCC, USB Power, Power, and PUSB. On wiring it's always red. Ground may be called: G, GND, Ground, and GUSB. D- may be called: USB-, USBP-, D-, or just -. D+ may be called: USB+, USBP+, D+, or just +.
To complicate things a bit more you'll probably notice that there's a number before each one. Take a look at the picture above from the USB hookup diagram for the A7M266.
You'll see that Asus decided to number the middle pins. On the first row (starting with pin 1, and marked with a 1) you'll find that they list D- as USBP2-, and D+ as USBP2+. The number 2 tells you a few things. First off: It's the 3rd USB port on the motherboard (they started numbering at 0), second it tells you that that D- and D+ must be used for the same port. Case manufacturers are just as likely to number their ports differently.
Take a look once again at the 4-pin joined picture:
Notice that you're D-'s have either a 1 or a 2 on them. These also tell you that they are part of the same USB port. (Remember, 1 port has 4 required wires). The numbering on the connector and the numbering on the header doesn't have to match.
To connect everything grab the following connectors: a same number D pair, (D-, D+), 1 power, and one ground. If your power and ground are numbered make sure all 4 are the same number.
Tip: Most cases that use all separated pins will bundle these together for you to make it easier.
Now, take your Power, D-, D+, and Ground and line the connector up with the appropriate 4 header pins on your motherboard. The header pins will be in a row under the Intel style, and in the Gigabyte style it will either be a row of 1 pin, a gap, and then 3 pins, or 3 pins, a gap, and then 1 pin. Press the connector down over the header pin and make sure it's firmly attached. Once you have done this go back and grab another set of connector wires (Power, D-, D+, Ground), and hook up your second front USB port. If your case has more then 2 front USB ports, and your motherboard has more then one front USB headers, then repeat the above as necessary.
Example: If you were hooking up the front USB on a A7M266, on a case with the pictured 4-pin joined connector type then: VCC lines up with USB Power, USBP2- lines up with USB1-, USBP2+ lines up with USB1+, and GND lines up with GND. For port 2, VCC lines up with USB Power, USBP3- lines up with USB2-, USBP3+ lines up with USB2+, and GND lines up with GND.
- If you are not sure what each header pin does then look back up at my definition of the header layouts. There you will find the common diagram.
- D- will almost always be closer to Power then Ground. D+ will almost always be closer to Ground then to Power.
- If you have a Intel standard USB layout, the missing pin is almost always pin number 10. The first pin, for the first USB row is almost always pin 1. The first pin for the second row is either pin 6 or pin 2 depending on who made the board.
- If you have a connector marked "shield" this is essentially your extra ground. Normally you will not use it.
- I tried hooking everything up but it isn't work. What should I do? Make very sure that you line up both D- and D+ properly! If you reverse D- and D+ then the device attached to the front USB port will not function. (fairly easy to do with Lian-Li layout) If you mistakenly connect a power wire where you should have a D- or D+ you could potentially damage the attached device. The same goes if you do not use the same numbering for the D- and D+. (you try to put a D- ment for one port, with a D+ for another port).
- The new wire do not match the diagrams on the website. My new usb hearder has red,orange,yellow and black?... Unfortunantely, not all case manufacturers use the official color codings for their actual wiring. Whenever possible you should use the markings on the end of the wires and NOT the coloring. If you have only the coloring to go by then you can you can normally assume that VCC is red. From there you can normally find D- because it's the wire closest to VCC. Ground is also normally Black and D+ is normally closest to Ground. Pretty much any color could be used for D- or D+. One fairly common no standard configuration is Red (VCC), Orange (d-), Yellow (d+), Black (Ground).
- I have a Gigabyte motherboard, but my case has a all joined connector for the Intel style header. What can I do? Unfortunately, there's not a really easy solution. What you'll probably want to do is cut off the connector from the wires and re-tail each wire. You'll need to locate crimpable connectors for .025" header pins, which are spaced .100" apart, plus a crimper for them. One other thing you can do if you have an old case you don't mind cutting apart is steal pre-tailed leads for things like power supply LEDs / case switches / etc, and solder the wires to them in order to create a messy looking but functional solution.
- I have a case that uses header connected front USB, but my motherboard doesn't have a front USB header. Do I have any options that still let me use those original front USB ports? If you do not have a free front USB header on your board, but still want to use front USB, it's theoretically possible to create a connector -> standard USB port cable. To do so you would need to cut open a standard USB cable and tail each wire with .025" square post header pins. You would need an appropriate crimper, and a source for the pins. They may be located at some larger electronic parts places. You could also potentially scavenge the header pins. One potential source is to find and install a USB card that has an internal header.
- Is the front USB of case (insert name here) compatible with USB 2.0? If a case has front USB, then you can use it for both USB 1.1 and USB 2.0, as long as you hook the connectors from the case to a front USB 2.0 header. If you hook the connectors to a standard front USB header (1.1) then you will only get USB 1.1 on your front ports. The wiring for USB 1.1 and USB 2.0 is essentially the same so existing cases can use either standard, provided the motherboard supports the standard you want to use.
Updates / Additional Tips:
- A few motherboards have the Intel style pin arrangement without the missing key pin (10).
- Extra care should be taken when connecting front USB on a motherboard that also has headers for Firewire (IEEE1394). The header for Firewire/IEEE1394 on a motherboard may look very similar / identical to the Intel Style USB connector. Make sure you have the right header.
- A few internal usb cables have a small plate / key on the back of the connector that you can use to switch the wire order in the connector. It's not always present though so I didn't mention it before hand. If you are stuck in a sitation where you'd have to cut off the entire connector and re-tail it then you may want to check for this. In most lower / mid range cases you will not find the plate / key. In higher end cases you are more likely to find it. -- I would like to stress that you would only need this in a extreme situation such as a stange non-standard connector arrangement + a Intel / Gigabyte all joined connector.