🚀 go-pugleaf

A while ago there was a posting stating that it is possible to write
on a disk with the write-protect hole open (write-protected).  Most of
us were skeptical, wanting to see schematics to know if this was, in
fact, possible.

I have not seen any schematics, but I have witnessed, first-hand, a
write-protected disk being altered by a program.

The program is the Atari CP/M-Z80 emulator, which I downloaded from
GEnie.  I had write-protected the "system" disk to prevent mistakenly
deleting files during a previous operation, and had forgotten to
write-enable it again.  I gave the CP/M "era" command to delete a file
from the disk.  The disk made some *very* unusual sounds, and I got an
error from the emulator indicating that the disk was bad ("BDOS error
on A: bad sector").  I tried again; same result.  When I did a "dir",
the file was gone.  I removed the disk from the drive, to look at it,
and was shocked to discover that even though it was still
write-protected, the emulator had succeeded in deleting the file!

Now, I don't claim to know at what level the CP/M emulator is driving
the hardware.  Since the CP/M emulator writes its own disk format,
it's probably doing physical I/O via "rwabs" at least.  It's possible
that you can't get this behaviour through the normal TOS calls; I
simply don't know for sure.

I can tell you this, though: I'm going to be a lot more careful about
what I do, even if the disk *is* write-protected.  No smiley.


Longish .signature follows.  Skip now, or don't complain!

Greg Wageman			DOMAIN: greg@sj.ate.slb.com
Schlumberger Technologies	UUCP:   ...!uunet!sjsca4!greg
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(408) 437-5198			GEnie:  G.WAGEMAN
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