7 Aug
2007
7 Aug
'07
11:22 a.m.
I was looking at a bunch of Tandon TM100-4M floppy drives that I've
had for a (very) long time and saw something that never registered
with me before.
On the underside of the disk release latch (on the faceplate), a
small silver sticker. Most say "100 TPI DSR", but about one in every
4 says "96 TPI DSR". All drives are 100 TPI TM-100-4Ms, BTW as
identified on the body sticker.
Cheers,
Chuck
7 Aug
7 Aug
2:55 p.m.
On Tue, 7 Aug 2007, Chuck Guzis wrote:
I was looking at a bunch of Tandon TM100-4M floppy
drives that I've
had for a (very) long time and saw something that never registered
with me before.
On the underside of the disk release latch (on the faceplate), a
small silver sticker. Most say "100 TPI DSR", but about one in every
4 says "96 TPI DSR". All drives are 100 TPI TM-100-4Ms, BTW as
identified on the body sticker.
I have a few 100tpi Tandons (TM100-4M), that do not have a tpi sticker,
and that are clearly labeled TM100-4 (NOT 'M'!) on the body sticker. Did
somebody piece together a bunch of random parts? Or was Tandon really
sloppy about labels?
--
Grumpy Ol' Fred cisin at xenosoft.com
4:17 p.m.
On 7 Aug 2007 at 11:55, Fred Cisin wrote:
I have a few 100tpi Tandons (TM100-4M), that do not
have a tpi sticker,
and that are clearly labeled TM100-4 (NOT 'M'!) on the body sticker. Did
somebody piece together a bunch of random parts? Or was Tandon really
sloppy about labels?
Probably the latter. I've got one with an option number label, with
part crossed out and new numbers handwritten in.
I've got a couple of MPI 100 TPI drives that now lack any sort of
label (even the tach strobe on the spindle pulley is gone). I
attribute this to CDC using a lousy adhesive. I wish I could
remember the model number of these beasts--but all the sticky bits
are gone...
Did anyone ever make a half-height 100 TPI drive? I'm guessing "no".
Cheers,
Chuck
8:51 p.m.
On Tue, 2007-08-07 at 08:22 -0700, Chuck Guzis wrote:
I was looking at a bunch of Tandon TM100-4M floppy
drives that I've
had for a (very) long time and saw something that never registered
with me before.
On the underside of the disk release latch (on the faceplate), a
small silver sticker. Most say "100 TPI DSR", but about one in every
4 says "96 TPI DSR". All drives are 100 TPI TM-100-4Ms, BTW as
identified on the body sticker.
Perhaps there's not *that* much difference between 96tpi and 100tpi?
Possibly within the margin of error of the mechanism?
Gordon
9 Aug
9 Aug
12:25 p.m.
On 8 Aug 2007 at 1:51, Gordon JC Pearce wrote:
Perhaps there's not *that* much difference between
96tpi and 100tpi?
Possibly within the margin of error of the mechanism?
Almost certainly not. 100 tpi and 96 tpi drives locate cylinder 0 in
a different place--and over 77 cylinders, the difference is
substantial. My guess is that the faceplates came prelabeled and the
factory guys just grabbed the 96 tpi faceplates when they ran out of
100 tpi ones.
Cheers,
Chuck
10 Aug
10 Aug
5:10 a.m.
On Thu, 9 Aug 2007, Chuck Guzis wrote:
On 8 Aug 2007 at 1:51, Gordon JC Pearce wrote:
But the track-to-track distance is practically the same, at least I could
perfectly read all my SORD M23 disks in a standard DSHD drive (with tracks
0-2 obviously missing at the beginning). The M23 disks are 100tpi SS MFM,
the drives used are TEAC FD-50C.
Christian
Perhaps there's not *that* much difference
between 96tpi and 100tpi?
Possibly within the margin of error of the mechanism?
Almost certainly not. 100
tpi and 96 tpi drives locate cylinder 0 in
a different place--and over 77 cylinders, the difference is
substantial. My guess is that the faceplates came prelabeled and the
12:56 p.m.
On 10 Aug 2007 at 11:10, Christian Corti wrote:
But the track-to-track distance is practically the
same, at least I could
perfectly read all my SORD M23 disks in a standard DSHD drive (with tracks
0-2 obviously missing at the beginning). The M23 disks are 100tpi SS MFM,
the drives used are TEAC FD-50C.
Well, let's do the math. At 100 tpi, a track occupies a zone inside
of a band .0100 inch wide. At 96 tpi, a track occupies a band .0104
inch wide. While this may not seem to be a lot, consider that 77
tracks at 100 tpi will occupy a band 0.7700 inches wide, while at 96
tpi, the same number of tracks occupy a band .8021 inches wide. That
means that the 77th track will be 0.0321 inches off--more than 3
tracks' worth at 100 tpi. So, while you may have been able to read
much of the first part of your disks, I suspect that the inner tracks
did not read at all.
Cheers,
Chuck
3:34 p.m.
New subject: 100 v 96 (was: Tandon TM-100-4M curiosity
On Fri, 10 Aug 2007, Christian Corti wrote:
But the track-to-track distance is practically the
same,
By the time that you go 77 or 80 tracks, you are at least three tracks
away from where you want to be! That is NOT practically the same for this
use.
at least I could
perfectly read all my SORD M23 disks in a standard DSHD drive (with tracks
0-2 obviously missing at the beginning). The M23 disks are 100tpi SS MFM,
the drives used are TEAC FD-50C.
All of the Sord disks that I've seen have been 96tpi.
--
Grumpy Ol' Fred cisin at xenosoft.com
4:32 p.m.
New subject: 100 v 96 (was: Tandon TM-100-4M curiosity
On 10 Aug 2007 at 12:34, Fred Cisin wrote:
By the time that you go 77 or 80 tracks, you are at
least three tracks
away from where you want to be! That is NOT practically the same for this
use.
I've wondered on and off for awhile (20 years or so) if a Drivetec
drive could be reprogrammed to handle 100 tpi disks. Never got the
motivation to look into it. Sigh.
Cheers,
Chuck
4:48 p.m.
New subject: 100 v 96 (was: Tandon TM-100-4M curiosity
On Fri, 10 Aug 2007, Chuck Guzis wrote:
I've wondered on and off for awhile (20 years or
so) if a Drivetec
drive could be reprogrammed to handle 100 tpi disks. Never got the
motivation to look into it. Sigh.
A representative of Amlyn claimed that their drive could do both ("closed
loop analog servo") I never got around to trying, and no longer have
those drives.
--
Grumpy Ol' Fred cisin at xenosoft.com
8:47 p.m.
New subject: How accurate does a drive stepper need to be? (was: 100 v 96 (was:
Some imprecise numbers that might help to get a feel for it:
48 tpi is about 2 tracks per mm, or 1/2 mm per track.
Each track is about 1/3 mm wide down the center of that 1/2mm space that
is allocated to it.
96tpi is about 4 tracks per mm, or 1/4 mm per track.
Each track is about 1/6 mm wide, down the center of that 1/4 mm space that
is allocated to it.
There is absolutely no chance for a successful read if the positioner is
more than 1/2 track off.
--
Grumpy Ol' Fred cisin at xenosoft.com
13 Aug
13 Aug
5:42 a.m.
New subject: 100 v 96 (was: Tandon TM-100-4M curiosity
On Fri, 10 Aug 2007, Fred Cisin wrote:
> at least I could
> perfectly read all my SORD M23 disks in a standard DSHD drive (with tracks
> 0-2 obviously missing at the beginning). The M23 disks are 100tpi SS MFM,
> the drives used are TEAC FD-50C.
All of the Sord disks that I've seen have been
96tpi.
Hm, what SORD disks? There were modern SORDs like the M68K and the newer
version of the M243 that had standard 5.25" drives, they were low profile
desktop machines from the mid-80s. The SORD M23 is from 1982, the external
FDD is a SORD FD-20 that contains two TEAC drives.
I must admit that I had't tried to read *all* tracks, I had only read
some random tracks across the disk with AnaDisk. I've just done a SCAN of
the disk now. It starts with a difference of three tracks (track 0 is read
with track ID 3 and so on) and finishes with a difference of six tracks
(track 73, track ID 79). There are three areas where the drive sees some
sectors of one track and some of the next track (e.g. at track 42 it sees
sectors from track 46 and from track 47), partially with read errors.
BTW the disks are single-sided, MFM, 16 sectors/track (1-16), 80 tracks,
interleave 2:1.
Christian
6189
days inactive
6195
days old
11 comments
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cc＠corti-net.de -
cclist＠sydex.com -
cisin＠xenosoft.com -
gordon＠gjcp.net