Keyboard/mouse interface

PS/2 systems introduced a new specification for the keyboard and mouse interfaces, which are still in use today and are thus called "PS/2" interfaces. The PS/2 keyboard interface was electronically identical to the long-established AT interface, but the cable connector was changed from the 5-pin DIN connector to the smaller 6-pin mini-DIN interface. The same connector and a similar synchronous serial interface was used for the PS/2 mouse port. Additionally, the PS/2 introduced a new software data area known as the Extended BIOS Data Area (EBDA). Its primary use was to add a new buffer area for the dedicated mouse port. This also required making a change to the "traditional" BIOS Data Area (BDA) which was then required to point to the base address of the EBDA.

[edit] Graphics

Most of the initial range of PS/2 models were equipped with a new frame buffer known as the Video Graphics Array, or VGA for short. This effectively replaced the previous EGA standard. VGA increased graphics memory to 256 KiB and provided for resolutions of 640×480 with 16 colors, and 320×200 with 256 colors. VGA also provided a palette of 262,144 colors (as opposed to the EGA palette of 64 colors). The IBM 8514 and later XGA computer display standards were also introduced on the PS/2 line. Although the design of these adapters did not become an industry standard as VGA did, their 1024×768 pixel resolution was subsequently widely adopted as a standard by other manufacturers, and "XGA" became a synonym for this screen resolution. The PS/2 Model 25 and Model 30, however, did not include VGA. On these budget models, IBM opted to use MCGA, which was a stepping stone between CGA and VGA, but unfortunately lacked EGA compatibility.