Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!ut-sally!husc6!cmcl2!rutgers!cbmvax!grr From: grr@cbmvax.UUCP (George Robbins) Newsgroups: comp.sys.amiga Subject: Re: An Amusing Anectode (The tale of the 2 Meg disk) Message-ID: <2119@cbmvax.UUCP> Date: Wed, 15-Jul-87 07:29:56 EDT Article-I.D.: cbmvax.2119 Posted: Wed Jul 15 07:29:56 1987 Date-Received: Fri, 17-Jul-87 06:13:53 EDT References: <398@rocky.STANFORD.EDU> <1649@cadovax.UUCP> <873@omepd> Reply-To: grr@cbmvax.UUCP (George Robbins) Distribution: world Organization: Commodore Technology, West Chester, PA Lines: 43 In article <873@omepd> hah@isum.UUCP (Hans Hansen) writes: > In article <1649@cadovax.UUCP> keithd@cadovax.UUCP (Keith Doyle) writes: > >In article <398@rocky.STANFORD.EDU> ali@rocky.stanford.edu (Ali Ozer) writes: > >>Anyway, now I have a 2.0 Meg capacity floppy disk. 8-) > > > >Well, if 2.0M 3.5" floppys achieve their high density in the same way > >HD 5.25" floppys do, you might not want to use it. HD disk drives use > >a higher write current, because the floppy media is less sensitive, which > >for some reason permits higher density. Normal disk drives will not > >put out a high enough write current to write the media reliably. I > >remember having all kinds of problems trying to format HD disks on > >non-HD drives until this was explained to me, and I gave up trying. > > > The new HI-Density Disks use PERPENDICULAR rather than PARALLEL magnetic > particle alignment. The 2Meg floppy doubles the track count or has 160 > cylendars. Upgrading the A1000 with a 2Meg drive while sounding neet > and deliver more bytes for the buck, unless commodore gets on the band > wagon (HINT HINT), will cause a compatibility nightmare. What I would > like to see is a driver that can recognise both types of drives and > automatically adjust the cylendar count. > > Hans Oh, confusion! 8-( The new 1.44 MB drives used on the IBM PS/2 machines don't use perpendicular recording, this is still pretty much off in the future. They don't have more tracks, rather they do use the 500KB/s data rate like the 8" floppies and AT 1.2 MB drives to increase the bit density on a track and get more sectors/track. They do require special hi-density diskettes, which have a higher magnetic coercivty, meaning they need a stronger magnetic field for writing/erasure, but can, in effect, support writing "smaller" bits on the disk. In any case, the floppy controller section of the Amiga chipset does not currently support a 500KB/s data rate in MFM mode, making the issue kind of academic at this point. You might be able to accomplish something in the "Apple GCR" mode, but as I understand it, there is considerably more software bit manipulation in the read/write process that would probably make this less attractive. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)