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From: johne@hpvcfs1.HP.COM (John Eaton)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 3.5" High-Density Woes
Message-ID: <670017@hpvcfs1.HP.COM>
Date: 28 Aug 89 15:21:02 GMT
References: <1001@apctrc.UUCP>
Organization: Hewlett Packard, Vancouver, WA
Lines: 21

<<<<
< Actually it is the higher current causing self-erasure on the inner tracks
< because of the lower coercivity of the DD media.  Because the HD has higher
< coercivity we can resolve a "tighter pattern", but require the higher current
< to write.  It's not the retentivity that makes the real difference but that we
< have to pound on it much harder to make it accept the signal in the first
< place.
----------
I suspect that 3.5 inch drives use the media sense hole to determine what density
the media can support. Although IBM chooses to ignore this data, the drive 
probably doesn't and could use this information to set write current. 

This would add another dimension to the media fracas because it would make a 
difference in whether you formated on a PS/2 or used a hole punch. On a PS/2
you would write high density with low write current while using a hole punch
gives you high density using high write current. 



John Eaton
!hpvcfs1!johne