Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!uunet!brunix!dth
From: dth@cs.brown.edu (Dzung T. Hoang)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: HELP : DOS doesn't recognize a disk change
Keywords: 4dos,os/2,disk-change
Message-ID: <58112@brunix.UUCP>
Date: 30 Nov 90 21:09:02 GMT
References: <4419@ruuinf.cs.ruu.nl>
Sender: news@brunix.UUCP
Reply-To: dth@cs.brown.edu (Dzung T. Hoang)
Organization: Brown University Department of Computer Science
Lines: 38

In article <4419@ruuinf.cs.ruu.nl> hrbaan@cs.ruu.nl (Hayo Baan) writes:
>Hi there, I am having a HUGE (yes, HUGE) problem using 4dos on my '386.
>It all worked fine ..., until I installed OS/2 1.2 on my hard disk (with the
>dual boot feature offcourse). The problem is that when I change a floppy
>disk in one of the drives (A: = 1.44Mb, B: = 1.2Mb) 4dos doesn't recognise
>this, ie. if I dir it, all I get is the directory of the previous disk. This
>error goes even further : if I have NO disk inserted, I still get the same
>directory (allthough it reads the drive). But this is not all! If a insert
>a DD disk in the drive (and the previous was a HD disk) it reports a
>general failure!. For this, there is no other solution, then to reboot and
>to try again.
>
>My question : what has gone wrong, and what is the solution.
>
>Awaiting your responses,

I ran into a similar problem when I acquired an external CMS drive with
an 8-bit interface.  The interface has cables that allow it to be connected
between the floppy controller and the floppy drives.  After I installed the
interface, I began getting problems with the floppies, as described above.
After a long inspection of the tape drive interface, I found that the line
that has meaning RDY for XT's but different meaning for AT's and 386 (I
forgot the name of the signal) is hardwired to either high or low (I forget
details).  I removed a trace leading to that signal and added a switch in
place of the trace.  So when I wanted to use the tape drive, I would close
the switch, otherwise, I would leave it open.  Actually, I could leave it
open and the tape drive would still work.

So the problem you are having may be due to this RDY line.  Many floppy
drives have jumpers to select between the XT and AT signals for this line.
This could be what's causing the problems.

Now that I think about it, I think the AT signal that replaces the XT RDY
is the media change detect signal, which explains the above problems.
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Dzung T. Hoang
dth@cs.brown.edu
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