13 Oct
1999
13 Oct
'99
3:16 a.m.
From: jpero(a)pop.cgocable.net
To: classiccmp(a)u.washington.edu
Date: Wed, 13 Oct 1999 14:46:24 +0000
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Subject: Re: Floppy disks again
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Date: Tue, 12 Oct 1999 10:33:08 -0400
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Reply-to: classiccmp(a)u.washington.edu
From: allisonp(a)world.std.com
To: "Discussion re-collecting of classic computers"
<classiccmp(a)u.washington.edu>
Subject: Re: Floppy disks again
X-To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Yes, specifically head width. The media also
limits things some
as very narrow head will tend to dig into the media and the width of the
track also defines signal level. Zip disks are high track density
floppies using special cobalt media for high bit density and also high
track density. They aslo have servo info on the media to aid in finding
the rather narrow tracks.
The tolerences is very loose especially in zip harderned steel
wire-rails resting in vee notches basically clamped between black
chassis and clear piece by 4 T6 (wood) screws, the magnet poles
simply held together by magnetic power. Whole magnet thingy is
simply loose in it's holder and only kept in place by pieces of tapes
to prevent rattling. I rescused one from certain death after
cleaning the heads with piece of tissue paper clamped between heads
dampened with model glue fluid to clean both. Alignment is basically
built in (mostly in that black chassis and heads). Remaining
alignment errors is taken up by servo tracking alone.
Curious: What is ideal way for heads design? Make it larger to keep
it from digging into soft floppy cookies in those zip drives? Those
heads looks exactly like it came out of early 3.5" harddrives.
And ironically spun at 3600rpm.
This is why 135 tpi has been the limit for absolute mechanical positioners
like floppies. At some point the track is so narrow you have to be able
to hunt for it and stepper based positioners are inexpensive but lack
resolution (and speed) for that task. The next generation will be some
form of voicecoil and the media will have embedded servo (Zip, LS120,
Jaz and friends). At some point you bridge the differences between floppy
and hard disk.
Small bone: Jaz is harddrive technology w/ platter(s) in a cartidge
no different from Syquests and like.
Allison
Wizard