I recently bought a 24 year old IBM Model M keyboard. From what I gather, it'd been left on a shelf for the last 5 years, so you can imagine the amount of dust dirt and crap that was on it. Before cleaning it, I plugged it in to my laptop (running Fedora 17) using a PS/2 to USB adapter. What I found was, while it still works, the keys I press don't correspond to what is displayed on the screen. So for example, when I type S on the keyboard, I get ß display on the screen instead. At the time, I put this down to the adapter not working properly.
Since then, I stripped the keys off the keyboard and cleaned the whole thing. It looks like it's just come out of a box! I then plugged it in to my computer (also running Fedora 17) via a standard PS/2 plug. The computer loaded up to the login screen, and I typed in my password. Pressed enter, and I logged straight in to my machine.
At this point, I opened up a text editor and started typing some stuff. To my horror, the keystrokes I was entering weren't coming up as intended. What came up instead were characters that would map to the pressed key but only under a different keyboard language setting.
I opened up a program to see what keyboard language had been selected, and the correct one for the keyboard was selected (which is UK in my case). I opened up a window that would show what characters mapped to what keys, and I pressed every single key on the keyboard, and every corresponding block representing each key lit up. I went back to the text editor to try again, but I was still getting these random characters. Whats more is that the backspace key would not work, although in the other utility it would flash when pressed.
What I know is that at the login screen the keyboard must have entered the correct characters, otherwise I wouldn't have been able to log in. Further more, keys that don't respond while using a text editor as sending signals to the computer, as illustrated in that keyboard utility. The question is why random characters are displayed when they really shouldn't be? Would this be a hardware fault or a software issue?