Prototype IBM DemiDiskette drive

[Fred Cisin]

On Wed, 22 Aug 2018, Eric Smith via cctalk wrote:
> Unfortunately I don't recall the model number, but there was a Shugart 5
> 1/4" drive that made it at least to prototype and field test around late
> 1980 or early 1981. It was supposed to be really inexpensive, but almost
> plug-compatible with standard drives like the SA400. Unlike the SA390, it
> did have electronics.
> Instead of being built on an aluminum casting, it only had bent metal. The
> head stepping mechanism worked like an 8-track tape. It used a solenoid to
> advance one track inward; the only way to go outward was the next step from
> the innermost track returned to the outermost (track 0). The single track
> step time was incredibly slow; I think it was around 750ms, vs 40ms for an
> SA400.
> My employer at the time, Apparat, then famous for NewDOS-80 for the TRS-80,
> had one for evaluation, but decided not to resell them. It would have
> required special software support, which Apparat could have put in
> NewDOS-80. Presumably patches could have been offered for other TRS-80
> operating systems.
> I wasn't told what the retail price of the drive would have been, but I
> don't think it would have sold well even at 1/4 the price of an SA400.

Neat!
That could have given Exatron Stringy Floppy a run for the money!
Both in terms of CHEAP ("race to the bottom"), low-speed, and probably 
reliability.

Are you sure that that was 750ms track to track step, not 75ms?

There were a few 128K machines then.  Easiest patches to get around the 
ridiculously slow speed (going from track 17 (TRS-DOS directory) to track 
16 would require 750ms per track to 34 or 39, recalibrate (seek to 0, 
probably LESS than 750ms) and step 750ms per track from 0 to 16) would 
have been to cache a dozen tracks, particularly directory, in RAM.
'Course those opting for 128K would also spend the premium for a 
half-decent drive, . . .


It would also argue for the track 0 directory (PC-DOS, Mac, etc.) V the 
"seek center" track 17 of TRS-DOS, etc.

I wonder why Radio Shack didn't consider THAT for the CoCo?  They did 
everything else they could to sabotage it into being a home kids machine 
and avoid it being usable for anything further.  (chiclets keyboard, RF 
without composite video, 32 characters per line,  . . .  some of which 
could be fixed)


You will recall that the use of the QumeTrak 142 drive in "PortablePC" 
(5155) and PCJr required a change in PC-DOS 2.00 to 2.10 for slower step time.

--
Grumpy Ol' Fred     		cisin at xenosoft.com