Date : Tue, 15 Oct 1991 09:21:34 GMT
From : cis.ohio-state.edu!zaphod.mps.ohio-state.edu!wupost!csus.edu!csusac!sactoh0!ijpc!ianj@ucbvax.Berkeley.EDU (Ian Justman)
Subject: Re: general (Floppy Drives on the Xerox 820-II)
ritchie@hpdmd48.boi.hp.com (David Ritchie) writes:
> I think that these are probably hard sector drives, so the answer is
> 'no'.
Wrong, pal. There's no such thing as a "hard-sectored drive" in
the 5 1/4" world. Besides, ALL FM and MFM soft-secotred setups
have and use the said emitter-dectector pair. Even the IBM PCs
use them. That's how the hardware finds sector 1 on each track.
In the world of soft-sectors, it's called the "index detector";
in hard sectors, it demarcates each sector and says where the
track starts/ends.
The only thing that determines whether the disk is hard- or
soft-sectored, save the drive controller, is the disk itself.
The only soft-sectored drives that don't use the index/sector
hole that I know of are Apple II, Commodore, and Atari.
> To be certain, look for a hard sector detector/LED combo near the
> drive hub -- if so, the drive is hard sector.
Pure and total horse-hockey. FM and MFM soft-sectored systems
MUST use it to find the first sector. In soft-sectored world,
like I said, it's called the "index sensor". 3 1/2" drives use
it too, but it's built into the drive and the diskette itself
doesn't need the hole because the diskette lines up to the hub in
EXACTLY the same place every time. On the 5 1/4" disk where you
can't clamp onto a very specific place like you can with a 3 1/2"
and have it line up with the index, you MUST have part of the
indexing mechanism on the floppy diskette itself. And don't tell
me it doesn't. And if you try, tell me what that one hole on the
diskette (not the hub; the one where sectoring holes would
normally go) is for.
BTW, there's no such thing an an "IBM PC floppy drive". There
ain't no such thing. The interface is exactly the same as if you
had taken your disk drive from your Kaypro and plugged it into
your PC.
Ian Justman | ...!{ames|apple|sun}!pacbell_
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