11 Jan
2012
11 Jan
'12
6:20 p.m.
----- Original Message
Agreed; a confusing term which is why I put it in quotes, but unfortunately
the one folks usually use.
You've obviously seen a much wider variety of disks than I have and I don't
doubt that Cromemco used 'quad' disks somewhere, but I don't think the RDOS
on the FDC supports that format.
The signals that are relevant on the 34 pin connector are in parallel with
the equivalent signals on the 50 pin connector, so the controller doesn't
know or care which connector is being used. The extra 8" signals are not
relevant to the HD drives except for the /RY signal which is not used by
5.25" DD drives like the TM100 but is expected from an 8" drive and thus has
to be jumpered from (50)-22 to (34)-34.
m
Date: Wed, 11 Jan 2012 00:44:13 -0800 (PST)
From: Fred Cisin <cisin at xenosoft.com>
...
I meant that a 1.2M drive is a poor choice to use for
the Cromemco 5.25"
formats, as a substitute for his TM100, because, as you said, it is
really a small 8" drive instead.
It sounded like he was trying to use 1.2M drives for the 400K 5.25"
formats. That CAN be made to work, but introduces a few unnecessary
hassles.
Yes, you're right; it can substitute nicely for an 8" drive but not a 5.25"
DD drive.
If by
80track/double density you actually mean 'quad' density, that's not
really supported although if the drive also rotated at 300RPM instead of
360 then I suppose you could use 1/2 of it as a 360K DD disk.
I have seen 800K "quad" disks from Cromemcos. (I detest the term "quad
density", since it is double density with more tracks, resulting in quad
CAPACITY, but not quad density on the tracks.) If you want to
go to the trouble of making a 34<>50 pin adapter then
you're
good to go; on the other hand, the nice thing about the FDCs is that they
have both 34 pin and 50 pin headers, so as long as you connect the /ready
signal to pin 34 of the 34-pin header you can put all 4 drives on the
same
34-pin cable in any mix of 5.25DD, 5.25HD and 3.5HD .
I had heard (incorrectly?) that the 34 pin connector was only configurable
for the 5.25" data transfer rates (125K, 250K) V the 50 pin connector
being configured for the 8" rates (250K, 500K) >
Is that completely wrong? 
11 Jan
11 Jan
7:17 p.m.
> I meant that a 1.2M drive is a poor choice to use
for the Cromemco 5.25"
> formats, as a substitute for his TM100, because, as you said, it is
> really a small 8" drive instead.
> It sounded like he was trying to use 1.2M drives for the 400K 5.25"
> formats. That CAN be made to work, but introduces a few unnecessary
> hassles.
On Wed, 11 Jan 2012, MikeS wrote:
Yes, you're right; it can substitute nicely for an
8" drive but not a 5.25"
DD drive.
The FIRST 5.25" 1.2M that I had (purchased at a Silicon Valley swap)
was a pre-production? Mitsubishi 4854, that had a 50 pin connector,
and did not appear to internally support double stepping nor RPM
change for "360K" formats. Once I figured out that it was a 5.25"
8" drive, I had to have it, and paid more than $20.
The ORIGINAL 5170 implementation of always running 360RPM and
switching the data transfer rate from 250K to 300K meant that
SOME 1.2M drives were virtually impossible to use for double
density unless the controller expected them (and had the 300K
data transfer rate).
Later, the dual speed drives solved most of that.
BUT, those extras MIGHT throw in some complications for jumpering, etc.
Therefore, I'd still recommend getting the machine working using a
REAL 8" first.
I have seen
800K "quad" disks from Cromemcos. (I detest the term "quad
density", since it is double density with more tracks, resulting in quad
CAPACITY, but not quad density on the tracks.)
Agreed; a confusing term which is
why I put it in quotes, but unfortunately
the one folks usually use. You've obviously seen a much wider variety of
disks than I have and I don't
doubt that Cromemco used 'quad' disks somewhere, but I don't think the RDOS
on the FDC supports that format.
Unfortunately, I rarely saw the machines that sample disks came from!
And, users would rarely let me know if their system was modified from
the original factory setup. If I were to question them about changes,
many would insist, "EVERYBODY makes that change." It was hard enough
dealing with people who would insist that their Morrow disks came from
an "ADM3A computer". I was once given a "Pentabs" computer,
actually
a Vector-Graphic bundled and rebadged for Pentabs accounting software.
The signals that are relevant on the 34 pin connector
are in parallel with
the equivalent signals on the 50 pin connector, so the controller doesn't
know or care which connector is being used. The extra 8" signals are not
relevant to the HD drives except for the /RY signal which is not used by
5.25" DD drives like the TM100 but is expected from an 8" drive and thus has
to be jumpered from (50)-22 to (34)-34.
Great! So, when I was told that the signals were different, that was
COMPLETELY wrong (other than pinout of TG43, READY, etc.)
Thank you,
--
Grumpy Ol' Fred cisin at xenosoft.com
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