Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!wizvax!buscard!p5.f121.n324.z1.FIDONET.ORG!Kevin.Gmyrek
From: Kevin.Gmyrek@p5.f121.n324.z1.FIDONET.ORG (Kevin Gmyrek)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: How do I add a 3.5" 1.44M drive to my old XT?
Message-ID: <126.27FA60A4@buscard.FIDONET.ORG>
Date: 2 Apr 91 13:08:00 GMT
Sender: ufgate@buscard.FIDONET.ORG (newsout1.26)
Organization: FidoNet node 1:324/121.5 - The Business Card, Lawrence MA
Lines: 44


 > In article <12206@pasteur.Berkeley.EDU>
 > sadoyama@argon.berkeley.edu (Eric Sadoyama) writes:
 > >I've got an old Leading Edge Model D (an XT-compatible) that I'd like
 > >to add a 3.5" 1.44M drive to, either internally or externally.  I've
 > >been told that for various reasons, I can't do this.  Why?
 > >Is it the 8088 chip itself?  Is it the (Phoenix) BIOS?  Is it the floppy
 > >disk controller?  Or it it something that I haven't mentioned?  What do I
 > >need to upgrade in order to get this to work?
 >
 > I assume you have the XT's original floppy disk controller.
 > You'll need a new one which recognizes 1.44Mb drives.  Also, if
 > you're going for internal, make sure you have a spare power supply
 > lead and, of course, a free slot for the drive ;-)
 >
 > | Noam Mendelson    ..!ucbvax!web!c60b-1eq
 > |                   c60b-1eq@web.Berkeley.EDU

   Well, Noam,  it's not quite as easy as just that!  Let's assume 
that Eric's got a DOS version later than 3.3 which is the first
version that supported 1.44 Mb 3.5" floppy disks (720Kb supported
in DOS v3.2).
   In addition to this you also need to have an AT or PS/2 BIOS in order 
to support high density disks.  The PC and PC/XT BIOSs only support 
low density disks (360Kb 5.25" and 720Kb 3.5").  Although looking at 
the BIOS diskette calls (Int 13h) I think you might be able to get a 
1.44Mb disk working on an XT.  The AT BIOS contains functions to get 
and set the media type but on the XT those functions are not 
available.  The information comes from a disk parameter table whose 
address is stored in the vector for interrupt 1Eh.  I would assume 
that if you could set the proper value of 18 sectors per track (as
opposed to 9) into this table then you MIGHT be able to format a
1.44Mb disk.
   As far as reading and writing to this disk... who knows?

                                             Kevin

--- FD 1.99c
 * Origin: My two cents worth... (worth about 1.3 cents) (1:324/121.5)
--  
Kevin Gmyrek - via FidoNet node 1:324/121 (UUCP/UseNet<->FidoNet gateway)
UUCP:  wizvax!buscard!121.5!Kevin.Gmyrek
ARPA:  Kevin.Gmyrek@p5.f121.n324.z1.FIDONET.ORG
\wizvax!buscard!121.5!Kevin.Gmyrek