CMOS bad ? factory default settings
My somewhat educated guess is that it would work with any system carrying a
true Compaq BIOS and with an FN key.
I say "educated" because I once found a set of keystrokes to turn on a
software keyboard click on a Compaq XT-class system described in Peter
Norton's "Inside The IBM PC" book. To my complete amazement, it worked
perfectly on my then current laptop, a Contura 410C. I guess the code to
support that feature never was removed, at least not to that point.