PS/2 Extension and Adapter Cables

Telling the keyboard port from the mouse port

PS/2 uses a six-pin mini-DIN plug for both keyboard and mouse, so the plugs look identical. By convention the keyboard port is purple and the mouse port green, and an extension cable should go with the device it extends. Some boards have a single combo port that takes either, but on many boards a swapped device is not recognized. PS/2 is also not designed for hot-plugging: connect with the computer off, then start it, or the device may not be detected.

Extensions, adapters and the USB question

Extension cables are male to female, with the male plug at the PC end. The signal is a simple clock and data pair, so keep the total run short and avoid chaining several extensions. Adapters need care in both directions. A passive USB to PS/2 adapter works only with keyboards and mice that speak both protocols, which is common on combo devices. A PS/2 device on a USB port needs a converter with a chip inside. A few listings here are unrelated cables such as chargers or network patch cords, so make sure the title names PS/2 or mini-DIN 6.

Questions about PS/2 Extension and Adapter Cables

Can I plug a keyboard into the mouse port?

Usually not. The ports are wired alike, but the controller expects a specific device on each, so a swapped one often fails to work. Match purple for keyboard and green for mouse, unless the board has a combo port.

Why is my PS/2 keyboard not detected?

PS/2 is not designed to be hot-plugged. Switch the computer off, connect the keyboard or mouse, then power on. Also check that you used the right port and that the pins in the plug or extension are straight.

Will a USB to PS/2 adapter work with any mouse?

No. Passive adapters only work with dual-mode devices that can switch protocol, and these usually come with the adapter. A USB-only mouse in a PS/2 port needs an active converter.