HP drives

Holley, Michael michael_holley at mentor.com
Tue Dec 28 13:48:10 CST 2010

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.

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

> > 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
> On Mon, 27 Dec 2010, Christian Corti wrote:
> > HP used 35 for their 5.25" DS drives (e.g. HP82901) and 70 for their
> > 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
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.


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