Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!pepper!cmcmanis
From: cmcmanis%pepper@Sun.COM (Chuck McManis)
Newsgroups: comp.sys.atari.st
Subject: Re: high density 3.5" disks
Message-ID: <33643@sun.uucp>
Date: Wed, 11-Nov-87 16:04:48 EST
Article-I.D.: sun.33643
Posted: Wed Nov 11 16:04:48 1987
Date-Received: Sat, 14-Nov-87 04:48:57 EST
References: <2923@hcr.UUCP> <1940@dasys1.UUCP>
Sender: news@sun.uucp
Reply-To: cmcmanis@sun.UUCP (Chuck McManis)
Organization: Sun Microsystems, Mountain View
Lines: 19

The scoop on the high density drives is that they use a data clock that
is twice as fast as the low density drives. On Amiga/Atari/PC-XT type
5.25 and 3.5 inch disks this clock runs at 250Khz, on the AT and PS/2
this clock runs at 500Khz. Exactly double the speed, means you can fit
twice as many sectors on a track and double your storage (720K -> 1440K).
The standard Western Digital minifloppy only controllers will not read
or write this format. The WD1793 and family of dual 8"/5.25" controllers
will given they are supplied with the proper clock. Also, when you double
the bit rate you cram more bits in the same space so your drive mechanism
has to be able to resolve a higher number of flux changes/inch (fci) and 
the diskette has to be capable of retaining those flux changes faithfully.
So all you need are a new controller, drive, and diskettes and you're all
set. No I don't if anyone is planning on offering them for the above
mentioned computers (except the AT and PS/2 of course).


--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.