Intel Pentium Pro motherboard keyboard hang problem and fix

Larry M. Augustin (
Fri, 13 Dec 1996 19:03:03 -0800

Bug Report:

We have had reports of some models of keyboard becoming locking (no
response to any key press) under Linux 2.0.x kernels on Intel Pentium
Pro motherboards. Unplugging the keyboard and plugging it back in
again resets the keyboard and fixes the problem. We have been able to
duplicate the problem ourselves under kernels 2.0.12 and 2.0.25 with
the Intel VS440FX and PR440FX Pentium Pro motherbaords and the
Keytronic KB 101C Plus keyboard. The problem only occurs under Linux
(other OSes seem fine), and appears to only occur with very specific
motherboard and keyboard combinations.


The problem appears to be related to the keyboard rate setting in
arch/i386/boot/setup.S. If we comment-out the keybard rate setting
code, the problem disappears:

! Set the keyboard repeat rate to the max

! mov ax,#0x0305
! xor bx,bx ! clear bx
! int 0x16

We've started doing this. I don't have a BIOS reference handy, so I
haven't explored changing the parameters to the int 16 call.