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Newsgroups: comp.risks
X-issue: 8.62
Date: Fri, 21 Apr 89 23:24:14 -0400
From: henry@utzoo.UUCP
Subject: Re:  Writing on "write-protected" disks

>... Do RISKS
>readers know of other systems that are not protected at the hardware level?

It depends on what you mean by "at the hardware level".  Almost any system with
multiple heads (this includes most modern disk and tape) will find it difficult
to run the final write signal to the heads via the write-protect switch.  Any
other scheme introduces electronics between the switch and the heads, and those
electronics can fail.  Also, said electronics may well include firmware in
microcontroller chips -- is this "hardware" protection?  That aside, everything
I'm familiar with does the write-protect check at a level where user
programming can't affect it... but what horrors microcomputer companies will
perpetrate to save a few cents, only they and their customers can tell.  (As
witness the original IBM PC monochrome monitor, which software could burn out
by setting control registers improperly -- IBM borrowed the monitor from an
earlier product which wasn't user-programmable.)

                                     Henry Spencer at U of Toronto Zoology

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