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From: kpk@gitpyr.UUCP (Kevin P. Kleinfelter)
Newsgroups: net.micro.pc
Subject: Hard disk write protect
Message-ID: <1283@gitpyr.UUCP>
Date: Thu, 23-Jan-86 09:56:27 EST
Article-I.D.: gitpyr.1283
Posted: Thu Jan 23 09:56:27 1986
Date-Received: Fri, 24-Jan-86 09:19:45 EST
Distribution: na
Organization: Georgia Institute of Technology
Lines: 25

Recently there has been discussion of copy protection schemes trashing disks.
Another case where disks can get trashed is when the programmer is developing
software which may alter MS-DOS memory, and possibly causing invalid
directory information to be written to the disk.

On a floppy based system, these disasters are easy to avoid: you just
put a write protect tab on the endangered diskette, and test away (or just
make a quick backup).

These approaches are inappropriate for a hard-disk based system. (There
is no write protect notch, and a "quick" backup can take over an hour!)
You can argue that booting your hard-disk PC from a floppy means that MSDOS
doesn't know about the hard disk, and therefor won't update it erroneously,
but if I am writing software which mucks about with memory and IO ports,
I still might end up trashing my precious 20 megs.

Why doesn't anyone sell a hard disk with a write protect switch on the
front bezel?  What would be involved in adding one?  (I assume that
there must be a write enable line from the controller to the disk.  Would
I simply need to install a SPST toggle switch in this line, or would
it be more complex?)



Disclaimer of responsibility: I am irresponsible.