Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!att!mtuxo!mtgzz!drutx!druwy!dlm
From: dlm@druwy.ATT.COM (Dan Moore)
Newsgroups: comp.sys.atari.st
Subject: Re: Question on 1.44 meg drives...
Message-ID: <4159@druwy.ATT.COM>
Date: 28 Jun 89 15:06:23 GMT
References: <8906261817.AA17231@jade.berkeley.edu>
Organization: AT&T, Denver, CO
Lines: 39

in article <8906261817.AA17231@jade.berkeley.edu>, WSCART01@ULKYVX.BITNET says:
>  I suppose most of you are aware of 1.44 Meg drives out for the IBM. They
> use 160 tracks instead of the 80 tracks normal drives.

	The 1.44 Meg high density drives are not 160 track drives, they
are 80 track drives just like the STs.  The difference is in the number
of sectors per track (actually the bit rate on the disk is higher). 
Normally the ST uses 9 sectors per track, 10 sectors works reliably, 11
will work on drives that are spinning much slower than the spec says
(about 290 RPM instead of 300 RPM).  All these sectors are written with
a 2 micro-second bit interval.  The 1.44 Meg drives put twice as much
data, 18 sectors, on a track.  This is done by using a 1 micro-second
bit interval, a different magnetic coating on the disks which can
handle the higher bit rate, and a different head design on the disk
drive which can handle the stronger currents used to write on the
disks.

>						 The question i'm
> pondering is: Why has no one hooked one up to an ST? I suppose there is
> either a harware or software diffuculty to overcome. Does anyone know
> which, and exactly what the problem is?

	The ST floppy controller doesn't support the 1 micro-second bit
interval, it only supports 2 micro-seconds.  So you'd have to replace
the floppy controller with one that can handle both (you do want to
read your current disks don't you?), replace the current floppy with a
drive that can handle the high density disks and then re-write the BIOS
floppy disk code to support whatever floppy disk controller you
inserted.  Of course all the third party programs that go directly to
the floppy controller will break (Spectre 128, Twister, DCFormat,
etc.).




				Dan Moore
				AT&T Bell Labs
				Denver
				dlm@druwy.ATT.COM