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From: phils@tekigm.UUCP (Phil Staub)
Newsgroups: comp.arch,comp.periphs
Subject: Re: Re: an idea for higher capacity disks
Message-ID: <1017@tekigm.UUCP>
Date: Fri, 14-Nov-86 11:56:40 EST
Article-I.D.: tekigm.1017
Posted: Fri Nov 14 11:56:40 1986
Date-Received: Sun, 16-Nov-86 20:19:06 EST
References: <899@ethos.UUCP> <987@cbmvax.cbmvax.cbm.UUCP>
Reply-To: phils@tekigm.UUCP (Phil Staub)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 42
Xref: mnetor comp.arch:29 comp.periphs:13

In article <987@cbmvax.cbmvax.cbm.UUCP> daveh@cbmvax.cbm.UUCP (Dave Haynie) writes:
>  The PC-AT
>drives can store a bit more than this, but they do it by formatting around
>135 tracks per side, which requires special high-density diskettes instead
>of the standard DS/DD diskettes that an 8250 could use.
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Dave Haynie	{caip,ihnp4,allegra,seismo}!cbmvax!daveh

It is my understanding that the AT's high density drive is 80 tracks per side, 
but due to a higher bit density, made possible by the higher coercivity 
medium used, they are able to squeeze fifteen 512 byte sectors per track. 
This leads to the following calculation:

			  2 sides 
			* 80 tracks per side 
			* 15 sectors per track 
			* 512 bytes per sector 
			__________________________ 
			1228800 bytes (1.2 megabytes).

By way of comparison, the standard PC/XT floppy format gives the following:

			  2 sides 
			* 40 tracks per side 
			* 9 sectors per track 
			* 512 bytes per sector 
			__________________________ 
			368640 bytes (360k).




						

Phil Staub
Tektronix, Inc.
ISI Engineering
P.O. Box 3500
Vancouver, Washington 98668
C1-904, (206) 253-5634
..tektronix!tekigm!phils