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From: johnhlee@cory.Berkeley.EDU (John Lee)
Newsgroups: comp.sys.amiga
Subject: Hard/Soft Disk Write-Protect (was Re: Leaving Computer On)
Keywords: Amiga, Write-Protect, Disk
Message-ID: <12471@pasteur.Berkeley.EDU>
Date: 16 Apr 89 00:28:06 GMT
References: <7684@phoenix.Princeton.EDU> <11984@ut-emx.UUCP> <13123@louie.udel.EDU> <5277@cs.Buffalo.EDU>
Sender: news@pasteur.Berkeley.EDU
Reply-To: johnhlee@cory.Berkeley.EDU.UUCP (John Lee)
Organization: University of California, Berkeley
Lines: 34

In article <5277@cs.Buffalo.EDU> ugkamins@sunybcs.UUCP (John Kaminski) writes:
>Oh, BTW, I was wondering if write protect is harware or software enforced.  I
>had the ("lowly") Timex/Sinclair 2068 and something called a MikroDrive for
[...]
>tape after doing what I wanted.  The write protection was strictly managed in
>software by reading the status of another port, which had a bit of that port
>connected to a lever switch.  Without trashing one of my disks, is it possible
>to program the disk DMA, start the motor, etc. and write the disk with the
>tab on "protect?"  I am pretty sure on IBM-PC drives, the controller chip
>refuses to do it and puts a write-protect into its status register, thereby
>making write-protect more-or-less hardware enforced.  The only way you could
>do it is to change the firmware or microprogramming of the controller.
>What say you in netland?

The CBM drives and most floppy disk drives (that I know of) enforce the
write-protect *on the drive*; i.e., regardless of what the computer and
drive controller tells the drive to do, the drive will *not* write on
a write-protected disk.

But let me qualify that.  On my Heathkit H-89 computer (does anyone else
know what this is?  I still like this little outdated thing), one of my
drives is an Wangco-Siemans single-sided 40 track drive that can be
customized using jumpers and circuit board pads.  One of the traces can
be cut and jumpered so that the write-protect switch is ignored by the drive
and passed on to the controller only.  That means that it is up to the
controller to handle the write-protect and the drive will happily write
on a write-protected disk if told to do so.  However, the default was
to handle write-protect at the drive.  My other drive (a Tandon TM-400)
does not have this ability and always enforces write-protect, just like
my Amiga disk drives.
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