Some versions of BIOS's in motherboards do not correctly check the disk
change line, and some floppy drives do not support the disk change line.
In order to allow the floppy drive and system to correctly detect a floppy
change, especially when switching floppy disks of different densities, you
need to install this debug patch.  It should be done in yuor autoexec.bat
file as it needs to be done after every reboot.

The location 40:8f needs to be patched to a 01.  I am not a DOS user
and so don't really understand how to use debug in this manner, but this
is what needs to be done.