The PS/2 connector is used for connecting a keyboard and a mouse to PS/2-type computer systems. The mouse connector replaces the older DB-9 RS-232 mouse connector, while the keyboard connector replaces the larger 5-pin DIN used in the AT design. The keyboard and mouse interfaces are electrically similar with the main difference being that open collector outputs are required on both ends of the keyboard interface to allow bidirectional communication. Normal desktop motherboards will not identify the keyboard and mouse if they are placed on each other's sockets.

Laptops generally have a single port that supports either a keyboard or a mouse. Sometimes the port also allows one of the devices to be connected to the two normally unused pins in the connector to allow both to be connected at once through a special splitter cable. The mouse interface is somewhat different to RS-232 (which was generally used for mice on PCs without PS/2 ports) but nonetheless many mice were made that could operate on both with a simple wiring adaptor.

In the 386, 486 and Pentium era, the connectors were also seen on some PC clones with non-standard case designs and the PS/2 mouse connector was sometimes seen on a separate backplate on systems using a standard AT case. However PS/2 ports only became the norm much later with the introduction of the ATX form factor. The design decision for identical but incompatible connectors would prove aggravating to consumers. To help alleviate this, PS/2 keyboard and mouse connectors were later color-coded: purple for keyboards and green for mice as defined by the Microsoft PC 97 standard.

Today laptops and a large number of desktops do not include PS/2 ports and so the port is now regarded as a legacy interface. Many current keyboards and mice support both USB and PS/2 with a simple wiring adaptor and active adaptors are available which plug into a USB port and provide a pair of PS/2 ports.

Specifications

Connector

Pin numbers (looking at socket):

 **On some laptops mouse clock for splitter cable.

See also

• Bus mouse

External links

• PC mouse information
• PS/2 keyboard and mouse mini-DIN 6 connector pinouts

Computer peripherals