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From: allbery@NCoast.ORG (Brandon S. Allbery)
Newsgroups: comp.sys.mac
Subject: Re: SE question
Message-ID: <1989Oct19.230656.10686@NCoast.ORG>
Date: 19 Oct 89 23:06:56 GMT
References: <50037@<1989Oct2> <8400174@m.cs.uiuc.edu> <1989Oct12.231203.15676@NCoast.ORG> <670@wet.UUCP>
Reply-To: allbery@ncoast.ORG (Brandon S. Allbery)
Followup-To: comp.sys.mac
Organization: North Coast Public Access UN*X, Cleveland, OH
Lines: 43

As quoted from <670@wet.UUCP> by tempest@wet.UUCP (Ken Lui):
+---------------
| In article <1989Oct12.231203.15676@NCoast.ORG> allbery@ncoast.ORG (Brandon S. Allbery) writes:
| ...
| >(Why do Macs use variable speed drives?  Because 400K floppies are that much
| >nicer than 360K floppies (SS/DD), and 800K better than 720K (DS/DD).  (Do
| ...
| 
| It's interesting that you brought this subject up because a
| friend of mine has an IBM PC, and is using a program that
| reformats DS/DD disks to 800K and (either 1.2Mb diskettes --> 1.44Mb
| or 1.44Mb diskettes --> 1.6Mb).  So, it's possible to get the
| extra capacity with just fixed-speed drives.  Given this
| situation, is there a program or is it possible to patch the
| MacOS to give us increased storage capacity?
+---------------

I doubt it, since it's probably a limitation of the IWM.  The new SWIM chip in
the FDHD-equipped Macs might be able to handle it.

PCs get 400K/800K/etc. by increasing the number of sectors per track from 9 to
10.  The Mac, if I recall, uses variable sectors per track as a result of its
speed diddling.  This is the reason why most other machines don't understand
Mac disks.

+---------------
| BTW, that program is only needed to format the diskette, and once
| formatted, any drive can read it.  I always thought this variable
| drive speed was nice--400K on SS 3.5s and 800K on DS 3.5s--until
| I learned that the Amiga gets 880K on DS 3.5s.
+---------------

Chances are the Amiga pushes the limits on the disk's capabilities:  for
example, on many PClones you can get 42 tracks of 10 sectors (420K) on a
nominal 360K disk.

++Brandon
-- 
Brandon S. Allbery, moderator of comp.sources.misc	     allbery@NCoast.ORG
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