Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!mcnc!ecsvax!mjg
From: mjg@ecsvax.UUCP (Michael Gingell)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Adding 360K drive to AT clone: Help needed
Message-ID: <2543@ecsvax.UUCP>
Date: Mon, 12-Jan-87 08:51:54 EST
Article-I.D.: ecsvax.2543
Posted: Mon Jan 12 08:51:54 1987
Date-Received: Mon, 12-Jan-87 21:49:58 EST
References: <1037@cad.cs.cmu.edu>
Distribution: na
Organization: UNC Educational Computing Service
Lines: 20
Summary: Cut the trace to pin 34

In article <1037@cad.cs.cmu.edu>, ralf@cad.cs.cmu.edu (Ralf Brown) writes:
> 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 6 (I think) is used as the reduced 
write current control to tell the HD drives when to write to regular
360 K floppies.  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 thisis 
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 on the drive. All it takes is a sharp knife.  Jumper the drive as
number 1 (counting from 0), and away you go ....

Mike Gingell     ....decvax!mcnc!ecsvax!mjg