Computer Hardware - PS/2 keyboards
Computer Hardware - PS/2 keyboards
To have computers in the office, it would require input devices, such as a keyboard
Home PCs such as the Spectrum, Atari and Amigo had there keyboards built in
When PCs started to be sold in retail in 1984 they keyboard had a standard connector being the large audio style 5 pin DIN connector
About a year later, a Windows based desktop called GEM (Graphics Environment Manager) came around and required a mouse to use
The mouse originally used the very standard COMM based serial connection which was normally via a 9pin D-SUB connection
Even though the Atari ST ran the same windows GEM system, the PC style mouse would not work on the Atari ST or Commodore amiga as they had a proprietary communication even though the connector was the same
While in business in the very early 1990's i remember well this old style keyboard connection and used to have many serial style mice laying around.
In 1987 a standard was establish called PS/2 and was a mauve (pantone color 2715C) and green (pantone color 3395C) small 6pin mini din style connections used for both keyboard and mouse
Mauve was for the keyboard and green for the mouse, making both smaller and easy to identify which connection to use
The mauve PS/2 style connection is electrically identical to the older 5 pin DIN keyboards making the switch over very easy (same keyboard, having a new connector)
The green mouse however is not, moving away from a serial COMM based communication
Both PS/2 keyboard and mouse used a similar communication method, where the keyboard was in essence port 1 and mouse port 2, now used a proprietary
Both used a clock based protocol slightly biased to receive data from the keyboard or mouse but also was able to return data
The protocol is very similar to the old style serial connections, and allowed control of items like the CAPS LOCK indicator and those multi LED back lit keyboards
As the mauve keyboard connection was electrically identical to the old IBM AT 5pin DIN connection,
adapters were common to connect an old style keyboard to the newer 6pin mini din connector
Due to both keyboard and mouse using the same protocols, each only having an identifier to indication which channel to use
laptops started to emerge with a single 6pin mini din connector that had both mauve and green color as either a keyboard or mouse could be used
it would read the data channel and adapt the port accordingly
Later keyboard started appearing with both USB and PS/2 connections, mice shipping with USB then an adapter to plug in to the PS/2 port
These small adapters were only passive in that it was just a wiring change, the keyboard or mouse was able to communicate on both PS/2 and USB protocols
The adapters would not work on a USB mouse that did not have the PS/2 protocol built in (such as all keyboards a mice shipped today)
We disposed of all these adapters as really are of no use in todays technology
As of 2023 some system were still sold with the PS/2 connector even though is deprecated and considered legacy
Tthe reason for this is it allows companies to totally disable all USB ports, while still being able to connect a keyboard and mouse
Today all input devices are USB, which generally replacing both the PS/2 and serial connections
Although in manufacture serial is still used on the very old manufacture hardware
We have designed and sold conversation technology that will allow those old machines to communicate with a current WIndows 11 PC
remain working with there existing software
