Hi Guys I have Googled a bit, and Wiki. It seems easy someone should know. Is the only difference between an XT and AT keyboard the number of keys? I’m interested in compatibility. I have a Windows IBM PS2 keyboard which is working fine with a 5 pin DIN interface XT/AT socket in vintage computer. All I did was chopped the PS2 connector and soldered a DIN connector matching the pins. http://www.kbdbabel.org/conn/kbd_connector_ps2.png So I’m wondering what actually happened when you switched the XT/AT switch underneath an old keyboard that came with he 5 pin DIN connector? Cheers, Art.