28 Dec
2010
28 Dec
'10
11:48 a.m.
The original Shugart SA400 minifloppy (August 1976) only allowed 35
tracks. In early 1977 Wangco announced the Model 82 Micro Floppy that
allowed 40 tracks with new media.
Here is a photo of both disks.
http://commons.wikimedia.org/wiki/File:Verbatim_5.25_minidisk_tracks_197
8.jpg
Michael Holley
-----Original Message-----
From: cctalk-bounces at classiccmp.org
[mailto:cctalk-bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: Tuesday, December 28, 2010 10:45 AM
To: cctalk at classiccmp.org
Subject: Re: HP drives
heard
> On Sun, 26 Dec 2010, Chuck Guzis wrote:
> > I find it more interesting that some of the 135 tpi users selected
> > odd values for the upper limit. HP used 66, I think and Jonos
used
On Mon, 27 Dec 2010, Christian Corti wrote:
> HP used 35 for their 5.25" DS drives (e.g. HP82901) and 70 for their
3.5"
SS drives
(e.g. HP9121).
35 was, of course the original Shugart SA400. I guess that HP never about, nor believed in, the extension to 40 of the
"standard".
Years ago somebody tried to tell me that '35 track' 35.25" disks had a
smaller head slot than 40 track ones and they could never be formatted
to
40 tracks. Whs this ever true?
[Mind you, this was the same person who tried to convince me that
formatting the 'other side' of a single-sided disk could ruin the drive
head, although using it asa single-sided disk would cause no damage. I
cannot think how that could be true.]
Then, of course, 79 was simply doubling the SA400 "standard".
I assume that;s a typo. Every time I shift 100011 left by one bit I get
1000110, or 70...
Howeer, was there ever a 70 cylinder 5.25" drive? That is one that was
only designed to use 70 cylinders ? I mean a raw drive, not a
drive+controller like the HP units we're discussing.
-tony