The ST's operating system caches disk information. It
detects floppy disk changes by watching the write protect line. If
it hasn't detected a floppy disk being removed, it will use the
directory information in RAM. Some computers have faulty write
protect lines, and do not detect when a disk is removed. This is
quite dangerous, as your disks may become corrupted if you read
from a disk, replace it with a different one, and write to that
disk drive. [On a one drive system you can get around this problem
by constantly swapping between calling drive A: A: and B: which
forces GEMDOS to update the disk cache, but that is a nuisance.]
You can tell if your ST has this problem by opening a
DeskTop window, replacing the disk with a different one, and
pressing Escape. The window should be updated with the contents of
the new disk. [I am not sure what causes this problem, but I have
heard that it is somewhat common among new Megas. I wrote this
program for my (cheap!) nextdoor neighbor, whose 2 year old(?)
520STFM recently developed this problem.]
Anyway, this program will "Force a Media Change", meaning,
in essence, that the ST will always read from a disk before
writing to it. The program will take up around 1K of RAM, and may
be placed in an AUTO folder. If you want to use this program as a
(temporary?) solution, be sure to ALWAYS run it before doing any
disk I/O.
I hope this program helps somebody out there (besides my
nextdoor neighbor!), and if anybody knows the solution to the
problem (besides replacing the drive), please let me know. My
address is
Larry McConnell
97 North Road
Bedford, MA 01730
and my Genie addresss is L.McConnell. [Please send all donations
(hahaha hohohoho) to my street address. :-]