Path: utzoo!attcan!uunet!husc6!mailrus!ncar!ames!killer!gtmvax!dms3b1!dave
From: dave@dms3b1.UUCP (Dave Hanna)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Do all 3.5 inch drives use the same encoding
Summary: No, they don't
Keywords: MFM GCR
Message-ID: <160@dms3b1.UUCP>
Date: 14 Nov 88 22:07:06 GMT
References: <8811101847.AA22940@godzilla.eecg.toronto.edu>
Reply-To: dave@dms3b1.UUCP (Dave Hanna)
Distribution: na
Organization: Daltech MicroSystems, Dallas
Lines: 24

In article <8811101847.AA22940@godzilla.eecg.toronto.edu> leblanc@eecg.toronto.edu (Marcel LeBlanc) writes:
>	Can somebody tell me if Amigas, IBMs, 1581s (CBM 8-bit), and Ataris
>use a compatible encoding method for 3.5" disk sectors?  I expect
    This is from memory, so all details may not be accurate, but the answer
is No, they don't.  IBM's, and, I think, Atari's, use the industry standard
(standard even before IBM started using it) MFM (modified frequency modulation),
and use a gap between each sector to allow for speed variances and start/stop
recording uncertainty.  The controller in the Amiga has the ability to use
that format, but the standard Amiga format uses GCR (Group Coded Recording),
which is also what the Apple II used (not sure about Mac).  They also read 
and write an entire track at a time, which allows them to eliminate inter-
sector gaps, and get more data on a track (11 sectors, vs. 10 maximum if
you allow minimal gaps).
>Marcel A. LeBlanc	  | University of Toronto -- Toronto, Canada

Hope this helps.
    Dave Hanna


-- 
Dave Hanna,  Daltech MicroSystems    |  "Do or do not -- There is no try"
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