The PS/2 connector is used for connecting a keyboard and a mouse 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 RS-232 "serial mouse" connector, while the keyboard connector replaced the larger 5-pin DIN 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) will not be recognized by the computer. Also, wrongly connecting the mouse or keyboard into the incorrect PS/2 port can damage sensitive parts of the computer's motherboard.

Original PS/2 connectors were black. Later PC 97 color code was introduced. PC 97 made the keyboard port, and the plugs on compliant keyboards, purple; mouse ports and plugs were green. As of 2007, this code is still used on most PCs.

PS/2 ports are designed to connect the digital I/O lines of the microcontroller in the external device directly to the digital lines of the microcontroller on the motherboard. They are not designed to be hot swappable. Hot swapping PS/2 devices usually does not cause damage due to the fact that more modern microcontrollers tend to have more robust I/O lines built into them which are harder to damage; however, hot swapping can still potentially cause damage on older machines, or machines with less robust port implementations.

If they are hotswapped, the devices must be similar enough that the driver running on the host system recognizes, and can be used with the new device. Otherwise, the new device will not function properly. While this is seldom an issue with standard keyboard devices, the host system rarely recognizes the new device attached to the PS/2 mouse port.

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.

Color codes

The most lasting impact of PC 99 was that it set out the color code for the various standard types of plugs and connectors used on PCs. As many of the connectors look very similar, particularly to a novice PC user, this made it far easier for people to connect peripherals to the correct ports on a PC. This color code was gradually adopted by almost all PC, motherboard and peripheral manufacturers.

The game port is the traditional connector for video game input devices on an x86-based PCs. The game port is usually integrated with a PC I/O or sound card, either ISA or PCI, or as an on-board feature of some motherboards. Microsoft have discontinued game port support with Windows Vista, so it is probable that manufacturers will cease to produce boards with this connector. However, it's still entirely possible to provide third-party drivers that will work with the gameport.

Game ports use DA-15 connectors (also incorrectly called DB-15), and usually double as connectors for MIDI instruments. To use a game port with MIDI instruments, one requires an unusual cable with a male and a female DA-15 and two male 5-pin DIN connectors. The drivers and hardware for the game port midi capabilities are based around the now standard Roland MPU-401 midi interface (in UART mode only), and support most MPU-401 standard applications for Windows and DOS.

Some advanced gameport joysticks support more than 4 buttons (e.g. 6 or 8) but typically require a special device driver for the 6 buttons to work properly, since the gameport doesn't have actual hardware support for more than 4 distinct buttons.

This can be overcome by either using some normally "unused" pins or changing the joystick's circuits (and related software) in order to read a 4-bit state code from the 4 button inputs, thus giving up to 16 button combinations (albeit with some limitations e.g. some buttons may not be held down) or a combination of both techniques.

High-end gameport joysticks such as the Microsoft Sidewinder rely on multiplexing a proprietary data stream through the 4 standard button inputs and sometimes through the "unused" pins, achieving full support for a rather high number of buttons (e.g. 16 or 20) while special features such as daisychaining multiple joysticks, force feedback or joystick programming become possible in some cases.

The obvious drawback here is the need for using a special device driver in order to interpret the joystick input, and making its usage rather time consuming and operating system dependent, while the joystick is usually unusable without a special driver (unless multiple operating modes are supported).

Some hardware and DIY enthusiasts have found ways to connect a wide array of input devices to the gameport and even found other applications for it e.g. voltage or current measurement, simple interfacing and data acquisition etc.

Pin out
Pin 1	+5V	+5V DC
Pin 2	B1	Button 1
Pin 3	X1	X axis for joystick 1 (0-100 kohm)
Pin 4	GND	Ground for B1
Pin 5	GND	Ground for B2
Pin 6	Y1	Y axis for joystick 1 (0-100 kohm)
Pin 7	B2	Button 2
Pin 8	+5V	+5V DC
Pin 9	+5V	+5V DC
Pin 10	B4	Button 4
Pin 11	X2	X axis for joystick 2 (0-100 kohm)
Pin 12	GND	Ground for buttons 3 and 4
Pin 13	Y2	Y axis for joystick 2 (0-100 kohm)
Pin 14	B3	Button 3
Pin 15	+5V	+5V DC (sometimes unconnected)