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From: ralf@cad.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Adding 360K drive to AT clone: Help needed
Message-ID: <1038@cad.cs.cmu.edu>
Date: Mon, 12-Jan-87 14:58:08 EST
Article-I.D.: cad.1038
Posted: Mon Jan 12 14:58:08 1987
Date-Received: Mon, 12-Jan-87 22:52:15 EST
References: <1037@cad.cs.cmu.edu> <2543@ecsvax.UUCP>
Distribution: na
Organization: Carnegie-Mellon University, CS/RI
Lines: 29

In article <2543@ecsvax.UUCP> mjg@ecsvax.UUCP (Michael Gingell) writes:
>In article <1037@cad.cs.cmu.edu>, I write:
>> I have recently purchased an AT clone (see my previous post for a 
>> rave review) and am trying to add a second disk drive.  I have 
>> two TEAC 55B drives from my previous computer, but neither of them 
>> will work in the AT, either as drive A or drive B.  The drive which 
>
>The AT uses 2 additional lines to the floppy drives to support the
>special HD 1.2 Meg drives...
>...  Pin 34 is an output from each drive which tells
>the AT when a disk has been changed.
>
>Pin 34 is the culprit. Most pre-AT 360K floppy drives have this
>connected as an alternate drive 3 select. If you plug such an unmodified
>drive into an AT it will hang. You must either cut the wire to pin 34
>in the ribbon cable, or do what I did, that is cut the trace to pin 34
>
>Mike Gingell     ....decvax!mcnc!ecsvax!mjg

Thanks, Mike!  Disabling pin 34 did the trick.

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