Those of us who already comb gray hair surely remember very well a port that has been in disuse for decades and that, however, resigns itself to die. Logically, we are talking about PS/2, where the keyboards and mice were attached to it as a communication port with the motherboard. Interestingly, out of the two of them, the one to put it aside was the first, which was suspicious. These are the reasons why PS/2 was first eradicated from PC keyboards.
Well, it was a controversial issue that was pushed by several factors, the main one and curiously not at all expected (irony off) was the user himself, who took it upon himself, as has been happening with USB-A for decades, to give it a slow death until the manufacturers decided to dispense with it for technical and RMA reasons.
Keyboards and mice with PS / 2, a continuous fight
The truth is that the average user had no idea what to do with the PS / 2 beyond knowing that the mouse or keyboard was connected there. At first it was only the keyboard with the AT format that had this interface, while the mouse continued with RS-232but given the limitations of this and its disuse fell into oblivion, the mouse adopted the PS / 2 and that’s where the problems came.
At first there weren’t two colors to differentiate them as such, and that caused electrical problems on PCs because the PS/2 interface for the mouse was electrically different from that of the keyboard, since the latter was bidirectional.
The controllers on motherboards did not know how to interpret what had been plugged in as such and logically they ended up frying, leaving the PC without input ports.
The next step was to name the interfaces with colors and the connectors of the peripherals were also colored with them, greatly facilitating the use and avoiding errors, but there were those who did not even want to look behind the PC to connect them well, so board makers had to create protection circuits where the voltage was simply cut off when the PS/2 keyboard collector was not detected.
Is this the main reason?
Yes and no. It was one of the excuses, the other has to do with the frequency and its range, since we are talking about between 10KHz and 16.66KHz, where in addition the typing speed of the users began to rise and this began to be a problem since the keyboards began to implement Anti Ghosting and N-Key Rollover technologiesso they were not blocked as such and left a flow of data that was being overwhelmed more and more with depending on which users were very docile in handling keyboard writing.
This, coupled with the fact that USB became very popular, forced manufacturers to implement two controllers and two PS/2 ports for keyboard and mouse, which increased costs. The mouse, being serial and having less information per second, took longer to disappear, but before this, manufacturers integrated dual controllers, unifying both PS/2 ports for keyboard and mouse into one, increasing speed and preventing electrical cuts that unplugging meant hot one of the two (they were not Plug & Play).
Finally, the push of USB coupled with cost savings to a great extent and the need for shorter access times for gamers and professionals ended up killing PS/2 for keyboards in favor of much more generic, faster, electrically powered USB. simpler and above all without RMA problems due to its hot factor.
As mice evolved toward higher polling rates, more buttons, and faster speeds, PS/2 became obsolete, and mice quickly moved to USB, leaving behind this interface that has given us so much joy.
