Path: utzoo!utgpu!water!watmath!221.162.fido!Usenet_area_"Cs.I.Pc"
From: 221.162.fido!Usenet_area_"Cs.I.Pc"@watmath.waterloo.edu
Newsgroups: comp.sys.ibm.pc
Subject: Re: What are these?
Message-ID: <16233@watmath.waterloo.edu>
Date: 8 Jan 88 16:36:23 GMT
Sender: ugate@watmath.waterloo.edu
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From Usenet: cbosgd!mandrill!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.ibm.pc
Subject: Re: What are these?
Summary: disk formats
Message-ID: <922@neoucom.UUCP>
Date: 8 Jan 88 15:01:50 GMT
References: <1535@mipos3.intel.com>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 25


Typical 5-1/4 inch disk designations:

DD (Double Density):  360K formatted capacity (when both sides are
  used).  40 tracks, 9 sectors/track.  IBM also supports 160K/320K
  8 sector/track formats.

4D (Quad Density):  720K formatted capacity.  80 tracks, 9 sectors
  per track.

HD  (High Density):  (used on PC/AT) 1.2 meg fromatted capacity.
  80 tracks, 15 sectors/track.


A High Density drive can be made to read any of the above formats,
and usually write them.  High Density disks formatted to 360K or
720K can be *read* but *not written* to reliably by the other drive
types.  HD diskettes are sort of like trying to use metal cassete
tapes in a regular cassette player.

The DEC Rainbow also has a bastard 400K single-sided disk format
that uses 4D media.


--Bill

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