26 Mar
2000
26 Mar
'00
11:13 a.m.
It looks to me as though you're addressing the flux reversal density issue
rather than the track density issue. WHile they're related in terms of the
coercivity of the media, we're discussing a situation wherein the bit rates
with respect to the rotational speed are intentionally the same. It's the
heads and related circuitry, and only that, that are different, aside from
the mechanism used to generate twice the track density.
The same problem exists with my LS120 drive formatting a disketted and
subsequently expecting the normal 1.44 MB drive to resolve the data written
with the high-resolution head. The manufacturer warns about this. The
media are precisely the same, yet the problem of the "normal" head resolving
data written on a much narrower path and muddled with lots of adjacent
signal remaining behind because the high-resolution head can't erase more
than the middle of it still remains.
It doesn't take a rocket scientist to figure this out. You must keep
focused on the problem. The fcpi (flux changes per inch) remain the same,
and the rotational rate remains the same. It's just the head gap size and
the nominal signal-to-noise ratio that make the difference.
Dick
----- Original Message -----
From: Sipke de Wal <sipke(a)wxs.nl>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, March 26, 2000 4:29 PM
Subject: Re: Parallel port hard drives?
If reformatting a 360Kb on a 1.2Mb drive that already
has data formatted &
written with a
360Kb drive the following situation will occur if that floppy is
subsequently read
with a 360Kb drive.
the 48 tpi track will have an 96 track inside it
the 48 tpi drivehard will read average data from both the 48 and the 96
bits
inside it
=
######01010001010000100010000010000010##### <Old 360KB DATA 1/4 48tpi
track
######00000000000000000000000000000000##### <new formatted track 1/2
96tpi
track
######00000000000000000000000000000000##### <new formatted track 1/2
96tpi
track
######01010001010000100010000010000010##### <Old 360KB DATA 1/4 48tpi
track
=
|
+-------- Head position cannot distinguish
between 0 or 1
Furthermore the adjecent 48 tpi tracks will interfere with the 96data
cause
the encoded magnets will
will start to merge. (Big magnet domains will make inroads into smaller
over
time)
As Tony Duel stated: It may be important to know if the floppies were
brandnew or bulkereased (degaussed)
or if they were written with a 48tpi head before reformatting. If you
bulkerease them before reformatting
(reformat preferably several times) you may get away with it since you
will
not get the interference from old
data. and the new format will be stronger. You may also have to write
identical data several times but only
with the 1.2 kb drive. Any writing of data with a 48tpi drivehead will put
you back to square one.
I circomvented this situation with separate floppies. One to transfer data
from system A (1.2mb) to System B (360Kb)
and another (formatted on the 360kb drive) to bring data from B to A.
For a more permanent solution I would look for an extra 360 Kb drive
Sipke de Wal
----- Original Message -----
From: David Vohs <netsurfer_x1(a)hotmail.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, March 26, 2000 9:31 PM
Subject: Re: Parallel port hard drives?
> >Did you start with a bulk-erased (i.e. with a degausser) disk? And >is
it
a
let
real 360K
disk (and not a 1.2Mbyte one)?
-tony
Yes, it was a real 360K disk, I just reformatted it in Windows (it will you choose between 1.2Mb or 360 formats).
____________________________________________________________
David Vohs, Digital Archaeologist & Computer Historian.
Computer Collection:
"Triumph": Commodore 64C, 1802, 1541, FSD-1, GeoRAM 512, Okimate 20.
"Leela": Macintosh 128 (Plus upgrade), Nova SCSI HDD, Imagewriter II.
"Delorean": TI-99/4A.
"Monolith": Apple Macintosh Portable.
"Spectrum": Tandy Color Computer 3.
"Boombox": Sharp PC-7000.
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