pcpartsandcables support pages


Information on configuring and fitting internal USB cables


These pages provide the basic information you will need when fitting your USB cable.

We receive lots of questions from new users who are not sure how USB pin headers are used and why some USB devices have 4/5 pin connectors whilst others have 8,9 or 10 pins.

This pages gives a brief explaination of the way that USB devices are connected to the USB pin header on the motherboard.

If you want to skip this basic introduction and move on to the fitting instructions page click here

Motherboard style USB pin header connectors


Internal USB devices connect to the motherboard using 4 wires. These wires are normally red, white, green and black. Two wires (red and black) are used to provide power to the USB device. The other two wires (white and green) are used to transmit data between the motherboard and the device.

The 4 wires in the USB cable can be connected to the USB pin header found on most modern motherboards. This pin header is designed to support two independent USB devices. The header is usually two rows of 4 or 5 pins. Each row of pins is normally associated with a separate device as shown in the picture below.

Two device USB pin header



When installing USB devices a separate cable can be connected to each row of the USB pin header. Using separate cables allows you to place your devices at different locations in the computer case, for example in different drive bays.

Note each row of pins on the USB pin header works in exactly the same way as the standard USB A sockets found at the rear of your motherboard. The only difference is the way that the cable is connected to the motherboard.

The USB pin header on the motherboard is the equivalent of TWO standard USB A sockets.

USB Device connectors with 4 or 5 pins


If your device uses a pin header this will normally be a single row of 4 or 5 pins. These pins are normally connected by the USB cable to one row of pins on the motherboard USB header as shown in the picture below. Note that the device only uses one row of pins on the motherboard header leaving the other free for connecting a second USB device.

Two device USB pin header

If you do not have a free USB pin header on your motherboard you can use one of our adaptor cables to connect the device to a standard USB A socket. See the section at the bottom of this page.

USB Device connectors with 8 9 or 10 pins



Sometimes manufacturers will build two separate USB devices into a single unit. A common example of this is a card reader that also has a front panel USB port. In this case the unit will have a connector that has two rows of 4 or 5 pins.

Although, the two USB devices are both contained within the same unit, the devices themselves are independent. Each device needs its own separate connection to the motherboard USB header.

Normally the top row of pins on the device connector will be for one device in the unit and the bottom row of pins will provide the connector for the other device. The picture below shows an example of a unit with a card reader + front panel USB port. This unit has a 9 pin connector.

USB CARD READER + FRONT PANEL PORT EXAMPLE

These devices can also be connected to standard USB A sockets if you do not have a free pin header available on your motherboard See below.


Using adaptor cables


Most internal USB devices can be installed using a cable with pin header style connectors at both ends. There are some cases when you might need to use an adaptor cable. The most common problems are:-

  • You do not have a free USB pin header available on the motherboard.
  • Your devices use standard USB B or mini-b sockets rather than pin header connectors.
  • Your device is a memory stick or some other device that plugs directly into a USB A port.

    These problems can be solved by choosing a suitable adaptor cable. All you need to do is decide how you want the cable to connect to your motherboard and device.

    The options for connecting to the motherboard are :

  • Using a cable that connects to a USB pin header.
  • Using a cable that plugs into a standard USB A socket.

    The options for connecting to a device are :

  • Using a cable that connects to a USB pin header.
  • Using a cable that plugs into a standard USB B socket.
  • Using a cable that plugs into a standard USB mini B socket.

    To select an adaptor cable you simply need to choose a cable that has the appropriate connectors at each end of the cable.

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