Fred Cisin cisin at
Wed Aug 25 17:31:17 CDT 2021

>> For 100tpi, there also existed Tandon TM100-4M drives.  The M stood for
>> "Micropolis".   One of the TM100-4M drives that I had did not have the
>> 'M' on the label.

On Wed, 25 Aug 2021, Chuck Guzis via cctalk wrote:
> The early Micropolis 48 tpi drives (1015 Mod I) were spec-ed at 35 tracks.

That's what I thought, but I wasn't sure.  Thank you.

> The 100 TPI models (mod II) were 77 tracks.

Yes.  I had forgotten that.   Thank you.

> Later drives included both 100 TPI and 96 TPI (e.g. 1115-5 and -6). 
> For a 5.25" drive, a beast of one.  No wonder they quit making floppy 
> drives.

My 35 track Micropolis drive outlasted every other drive (shugart SA400 
had radial alignment issues, others had speed control, etc.) and the 
machine itself.  The lead screw positioner was kinda slow, but so was the 
spiral "record" of the SA400.

> Tandon was pretty sloppy with their labeling.  I've got a TM-100-4M
> that's identified as such on the body label, but the door latch handle
> has a "96 tpi" sticker.  Whatthehell, a bezel's a bezel, right?

So, that's TWO mislabels within a tiny sample.

> The 100 TPI models (mod II) were 77 tracks.
The first "1.2M" drive that I got was from a computer swap and was among 
projects and prototypes.  It looked like a production model, with no 
obvious board re-work nor jumper wires.  It had a 50 pin header, instead 
of a 34 pin card edge connector!  I tested it, and it did go to 80 tracks, 
but I heard that when IBM was developing the 1.2M drive, some at 
Microsoft wondered whether IBM was re-introducing 8 inch drives!

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