Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!gem.mps.ohio-state.edu!rpi!crdgw1!crdos1!davidsen
From: davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Overide of write protect on floppies
Message-ID: <1531@crdos1.crd.ge.COM>
Date: 2 Nov 89 14:06:48 GMT
References: <1454@minnow.sp.unisys.com> <1455@minnow.sp.unisys.com> <62764@psuecl.bitnet>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Organization: GE Corp R&D Center
Lines: 25

In article <62764@psuecl.bitnet>, c9h@psuecl.bitnet writes:

|  BTW:  I do not know of any disk drive that will physically permit you to
|  write to a write-protected disk.  In fact, many of them have physical locking
|  mechanisms to prevent this.

  Back in the days of 8" floppies I hacked a drive with a 3 position
switch such that in one position the write circuit was disabled by
forcing the write protect "ON", in the 2nd position the write protect
line followed the sensor (normal operation) and in the last position the
write protect was strapped "OFF" so I could write the disk with a tab in
it. I had appropriate red, yellow, and green indicators, too.

  Another note, back when disk vendors put in metal write protect tabs,
some drives detected the write protect by *reflecting* light off the
surface, rather than passing light through the notch. This didn't cause
a security problem because on 8" disks, like mag tape, the tab is an
*enable*, and the default is write protect. This meant that using black
tabs wouldn't let you write the disk. On 5-1/4" the sense of the notch
was switched to default write enable.
-- 
bill davidsen	(davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen)
"The world is filled with fools. They blindly follow their so-called
'reason' in the face of the church and common sense. Any fool can see
that the world is flat!" - anon