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Path: utzoo!aesat!bmw
From: bmw@aesat.UUCP (Bruce Walker)
Newsgroups: net.micro.pc
Subject: Re: AT disk controller
Message-ID: <613@aesat.UUCP>
Date: Fri, 9-May-86 08:12:00 EDT
Article-I.D.: aesat.613
Posted: Fri May  9 08:12:00 1986
Date-Received: Fri, 9-May-86 08:13:28 EDT
References: <333@pilchuck.UUCP>
Reply-To: bmw@aesat.UUCP (Bruce Walker)
Organization: AES Data Inc., Mississauga Ont., Canada
Lines: 28
Summary: only supports two "floppy devices"

In article <333@pilchuck.UUCP> del@pilchuck.UUCP (Erik ) writes:
|My current PC has a 3.5" micro disk attached to it. If I get an AT, I
|figure I'll need the 1.2M floppy, a 360k floppy, and I would hate to
|loose my 3.5".  Since the AT does not provide for an extra drive
|connector coming out the back of the thing, the question is: are the
|hardware select lines there and just no additional connector provided,
|or is it impossible?

The IBM-supplied AT controller (manufactured by Western Digital) has
drive select (and motor-on) signals for only two floppy drives of
either density.  The bits in the I/O register that were defined for
drives three and four on the PC/XT controller, are marked as "reserved"
on the AT controller.  If you felt adventurous, you could piggy-back
some 7438's on top of the existing circuitry and lash up an extra
connector, but it would be the definitive "hack job".

In a nut shell, and WRT the "official" controller: no, there are no
select lines, and no, there is no additional connector, but no, it is
not impossible, just very difficult.

Take a look at some third-party disk controllers, someone (maybe
Taiwanese) may have built just what you're looking for.

Bruce Walker     {allegra,ihnp4,linus,decvax}!utzoo!aesat!bmw

"Over here is the power supply for my new stereo ...
 and down here is where we store the spent fuel rods."