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From: gerardka@hobbes.ism.isc.com (gerard)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Diffs between DD & HD disks
Message-ID: <1991Apr16.022449.19593@ism.isc.com>
Date: 16 Apr 91 02:24:49 GMT
References: <1991Apr9.141703.5134@cs.dal.ca> <1991Apr11.005743.1000@zeus.mgmt.purdue.edu> <1991Apr11.033648.5311@ism.isc.com> <1991Apr15.021812.2745@bilver.uucp>
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In article <1991Apr15.021812.2745@bilver.uucp> bill@bilver.uucp (Bill Vermillion) writes:
> 
>Well now, I beleive that should be
>
>"A 1MB drive cannot completely saturate the mag coating on a 2MB
>diskette".
>
>World of difference there.
>

	Yes, there is a world of difference, but the quote is accurate,
	although I cannot verify it factually.
	The full quote from "Floppy (3.5" HD) Disk Quality Report"
	put out by MEMCON Corp., a diskette duplicating service:

"As Table 1 indicates, HD floppies differ from DD ones not only in physical
appearance but in the coating thickness and magnetic properties of their
media.  These differences mean that a 2MB recording head can't completely
saturate the magnetic coating on a 1MB disk.  A DD floppy should never
be subtituted for a HD one.  A DD diskette can not be reliably recorded
by a HD drive, even with the proper use of the reduced write current
required by the greater magnetic sensitivity of the DD formulation."

table 1 (partial)
				1MB DD		2MB HD
head gap (um)			1.7		0.7
coating thickness (um)		1.9		1.0
mag strength (Oersteds)		600-650		630-730

	MEMCON Corp.
	2410 South 156th Circle
	Omaha, NE 68130
	402-333-3100
	FAX 402-333-2029

	I can only suggest that you check with MEMCON directly if
	you know the quote is factually inaaccurate.

	Gerard