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A converter is a small device which translates the signals between two other devices. In the keyboard world, this is mostly used to get older keyboards to work on a computer which only accepts USB keyboards. Please note that a converter is not the same as an adapter! Converters contain computer chips and need to be powered (mostly through the USB port), while an adapter is simply a passive component adapting one cable/port to another.

Commercial PS/2 to USB converters

A whole number of converters exist to make PS/2 keyboards work on new computers. Here's a short overview of the most popular and reliable converters:

"Blue Cube" converter
"Blue cube"
Common converter with a single female PS/2 port and USB male port. Works for most keyboards and can be bought cheap. Known to work with keyboards that need more power, such as the IBM Model M, where cheaper converters fail. They never appear to be sold under a brand name, but most known blue cubes contain the same Cypress chip and decent firmware. These converters are rather ubiquitous and some keyboard shops even sell them with their keyboards[1].
Multimode USB "Adapter" — this is a keyboard-only inline converter that resembles a PS/2 socket connected to a USB plug; this was previously sold via group buy at geekhack and found to be very reliable.[2]
Belkin USB Dual PS/2 "Adapter"
The Belkin F5U119 series is a converter with ports for a mouse and keyboard, although two keyboards might work as well. Works with virtually all keyboards out there, but it is more expensive than the blue cube. Belkin have sold this product under a large number of similar model numbers, and the various models ship with different controller chips. Some of the controller chips used are notorious for resetting periodically: the keyboard will cease responding, followed by the lock LEDs flashing as the keyboard reinitialises. Ideally one should acquire a model that contains the same Cypress chip as used in the blue cube for maximum reliability and compatibility.

For those wishing to connect vintage keyboards to a modern computer (especially PC/AT boards), it is often necessary to purchase both the Cypress-based Belkin adapter as well as the blue cube, as the subtle differences between the two products affects compatibility.

Commercial USB to PS/2 converters

StarTech PS/2 to USB Keyboard and Mouse Adapter — allows a USB keyboard and mouse to be connected to the PS/2 ports on a computer

Commercial ADB to USB converters

Griffin iMate
The Griffin iMate is the most common and best-known ADB to USB converter.

DIY converters

It is possible to make a custom converter using a small microcontroller. These converters have a few benefits in that they allow to transform the input and output, e.g. to make your own macro keys or Fn layer.

The easiest way is to use a development board with an Atmel controller like the Teensy board for example.

Soarer's XT/AT/PS2 converter

A general-purpose converter with handy tools to customize they keymapping of the provided binary file. Only the source of the tools is available. The documentation can be found in a Geekhack wiki: [1]. See the forum thread for the download: XT/AT/PS2/Terminal to USB Converter with NKRO

NOTE: a Teensy should be sufficient for the firmware and some basic config files. If you want to do a lot of advanced stuff like macros and Fn layers, try the the Teensy++. Check the documentation for more info.

Hasu's USB Controller/converter projects

These projects are only available as source code: GitHub: tmk/tmk_keyboard. It is specially written for the Teensy development boards and keymapping must be done in the source files themselves.

A short overview of sub-projects:

HaaTa's Kiibohd Controller/converter projects

Only available as source code: Gitorious: Kiibohd Controller. It has a number of modules that can be re-compiled to support various obscure keyboard protocols. Designed to work as a converter or as a replacement controller depending on how the configurations are setup. Keyboard layouts and macros are configured on their one layer independent of the input scan module and output module. The framework is designed to support multiple output protocols, but currently only a basic 6KRO USB module is working.

Current list of supported protocols:


  1. online shop page for the blue cube
  2. geekhack — G80-1838HPU/01 Trouble