PS/2 CONNECTOR

The PS/2 connector is used for connecting some keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE-9 "serial mouse" connector, while the keyboard connector replaced the larger 5-pin RS-232DIN used in the IBM PC/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. If a PS/2 mouse is connected to a PS/2 keyboard port (or if a PS/2 keyboard is connected to a PS/2 mouse port), the mouse (or keyboard) may not be recognized by the computer depending on configuration.

Type	keyboard and computer mouse data connector
Production history
Designer	IBM
Designed	1987
Superseded	DIN connector and DE-9 connector
Superseded by	Universal Serial Bus
Specifications
Data signal	Serial data at 10 to 16 kHz with 1 stop bit, 1 start bit, 1 parity bit (odd)
Pins	6
Connector	Mini-DIN
Pin out
Female connector from the front
Pin 1	+DATA	Data
Pin 2	Not connected	Not connected*
Pin 3	GND	Ground
Pin 4	Vcc	+5 V DC at 100 mA
Pin 5	+CLK	Clock
Pin 6	Not connected	Not connected**
* On some laptops mouse data for splitter cable. ** On some laptops mouse clock for splitter cable.

Port availability

In the 386 and 486 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 during the Pentium era (1993-1997). 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.

Old 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 from 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 adapter.

PS/2 mouse and keyboard connectors have also been used in non-PC compatible computer systems, such as the DEC AlphaStation line, early IBM RS/6000 CHRP machines and SGI Indy, Indigo 2, and newer (Octane etc.) computers.

Today's laptops frequently do not include PS/2 ports and so the port is now regarded as a legacy port on Wintel, having been superseded by USB. Many current keyboards and mice support both USB and PS/2 with a simple wiring adapter and active adapters are available which plug into a USB port and provide a pair of PS/2 ports. PS/2 ports however, can still be found on modern desktop computer motherboards, although some newer motherboards have no PS/2-port or only the keyboard port. These PS/2 ports cause less problems when KVM switching with non-Wintel systems.