A frightening little bit of technology

Chuck Guzis cclist at sydex.com
Fri Sep 7 19:35:08 CDT 2007

On 7 Sep 2007 at 23:18, Tony Duell wrote:

> And yes, I am clueful enough not be be complaining they didn't work as HD 
> disks on a PC/AT. What I a talking about is formatting them as 80 
> cylinder disks on BBC micros, TRS80s, etc. 
> I assume it was something like an increased background noise level. I cna 
> think of no other explanation.

Dunno, but when we were selling our own-branded Dysan 100 tpi 
diskettes, I was told by the Dysan sales tech that the formulation 
was exactly the same as the 48 tpi versions; that only the 
verification process was different.  Maybe the UK got all of the 
floor sweepings; I don't know.

I do know that the certifiers used for DSDD diskettes were programmed 
to toss a cookie that verified fine on one side but not the other 
into the "about to become SSDD" media pile.

That's not to say that the occasional branded-and-certified-as-100-
tpi diskette failed to format either.  There was a reason that 
everyone had a flawing mechanism of some sort built into most 
operating systems.  And our application was a bit tougher than most 
as we were packing something like 950K in a 77cyl * 2sides *12sect * 
512bytes format using GCR and an elevated clock rate.  This was a 
couple of years before Osborne was putting, what, 90K on a 5.25" 


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