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From: burton@asdsun.larc.nasa.gov (John Burton)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: Original IBM XT's and drive-size-limitations
Message-ID: <1991Jun28.130945.4757@news.larc.nasa.gov>
Date: 28 Jun 91 13:09:45 GMT
References: <81555@eerie.acsu.Buffalo.EDU>
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Organization: NASA Langley Research Center, Hampton, VA  USA
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In article <81555@eerie.acsu.Buffalo.EDU> bforob@ubvmsb.cc.buffalo.edu writes:
>Hi.  I just got hold of an old IBM/XT with two 5.25 low density drives.  I'd 
>like to add two new drives, perhaps a high density 3.5 and a high density 5.25 
>drive.  Somehow, I remember hearing that the high density drives can't be used 
>on the older machines.
>
>Could someone confirm this and indicate how high (and why) we can go with these 
>older machines?
>
>Thanx a bunch,
>
>--Rob

Rob,
 You *can* install both the 5.25" 1.2mb drive and the 3.5" 1.44mb
drive in an IBM-PC/XT. I've done it and I think mine is an even older 
version of the XT (*1* 5.25 low density full height drive and *1* 10mb
full height hard disk - max 256kb on motherboard). There are two
things you *must* have besides the disk drives...you *must* have 
a high density controller (one that *specifically* states that it
will support 3.5" 1.44mb & 5.25" 1.2mb floppies on an XT class
machine). The controller that came with your XT would *probably*
not support the high density drives (assuming that you have an 
original equipment controller). These controllers are available from
many places for < $50 (I purchased one from JDR micro devices that I 
*know* works, and I purchased one from CompuAdd that I haven't installed
yet (for another machine)). The important thing is that these
controllers have on-board BIOS that takes over from the motherboard
BIOS when dealing with the floppies - the motherboard BIOS doesn't
have a clue about high density drives...

The other must is a current version of DOS (assuming you're using
DOS). You need to have PC-DOS (or MS-DOS) ver 3.3 or later to
support the high density drives, particularly the 1.44mb drive - 
I *think* the 1.2mb drive was supported in DOS3.2 or maybe even
3.1, but the 1.44 was not supported until the later version...
best bet, call EggHead and get your $40 upgrade to MS-DOS 5.0
(unless they've sold out), that *definitely supports the 
high density drives...good luck...

John

+--------------------------------------------------------------------+
| John Burton                                                        |
| G & A Technical Software                                           |
| jcburt@gatsibm.larc.nasa.gov                                       |
| jcburt@asdsun.larc.nasa.gov                                        |
| jcburt@cs.wm.edu                                                   |
|                                                                    |
| Disclaimer: Hey, what can I say...These are *my* views, not those  |
|             of anyone else, be they employer, school, or government|
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