IBM Keyboards
IBM Keyboards
Ever since its manufacture of its Selectric typewriters, IBM has been known for producing their own in-house switches and keyboards. In addition to the introduction of many innovations in switch designs, IBM is also responsible for developing the XT, AT, and 101-key layout.
IBM PC Keyboard and XT Layout
The IBM Model F XT Keyboard was produced for the original IBM PC and IBM PC XT. These keyboards feature Capacitive Buckling Spring switches and an 84-key XT layout. It used a 5-pin DIN interface which communicated over XT protocol, which lacked the ability to show lock lights.
IBM PC AT Keyboard
Upon release, the IBM Model F XT keyboard was criticized for an excessive number of "stepped" keycaps and having a cramped layout. In addition to updating this layout, the IBM AT keyboard featured lock lights and a new AT protocol which was incompatible with the XT protocol. This meant that XT keyboards could not be used on AT computers, and vice versa.
The new F AT layout only used stepped keycaps for the CONTROL, ALT and CAPS-LOCK keys, and separated the numeric keypad from the rest of the layout (the keypad was integrated into the rest of the keyboard previously). IBM was again criticized for changing the layout of the keyboard.
IBM Enhanced Keyboard and Model M
IBM again aimed to improve the layout of the keyboard and worked with various focus groups to design a more convenient layout. Two new function keys, F11 and F12, were added, and the function keys were moved to the top of the keyboard. The CTRL key was moved to the bottom left and its old position was used by the Caps-lock key. Other notable changes to the layout include a 2-unit backspace, a shorter spacebar, and a straight enter key in contrast to the L-shape and ISO-shape enter keys on the previous two layouts. This resulting 101-key layout would be used with the IBM PC AT, the IBM PS/1 series, and IBM PS/2 series computers. Unlike the F XT and F AT layouts, this new layout was received well and is still used on many keyboards today.
IBM also used this opportunity to again cheapen their switch design. Instead of having a capacitive assembly underneath the switches, IBM introduced a membrane design that works nearly identically to many modern rubber dome keyboards. These membrane buckling springs can be distinguished from their capacitive counterparts as they produce less pinging and have a slightly different key feel.