Re: Did Commodore cheat with the quad density floppies?

Den Fri, 4 Jan 2019 05:14:48 +0000 (UTC) skrev William Levak
<wlevak@SDF.ORG>:
> On Thu, 3 Jan 2019, Mia Magnusson wrote:
> > As I recall, some 48 TPI disks actually caused problems when used
> > as 96 TPI.
> >
> > A qualified guess is that once 96 TPI DD disks became rather common,
> > they just made that kind of disks and labeled some of them as 96 and
> > some as 48 TPI for market / pricing purposes.
> 
> What they were labeled as was determined by what they were tested
> as. The testing is the most expensive part of the manufacturing
> process.

In some cases the testing were only done up to the wanted capacity.
I.e. if a batch of something would yield 50% higher end and 50% lower
end products, but the market only wanted 25% higher end and 75% lower
end products, testing would in some cases only be done until the wanted
25% higher end were found, and then everything else were only tested to
the lower end standards.

Not sure if this ever did happen on floppys but it was surely used on
DRAMs. That way some of the slowest rated DRAM's might be able to run
much faster, while all other speeds in the same production run usually
are good for exactly what they are labeled at. (If there were a large
demand for some in-the-middle speed, chips labeled at that speed might
also only had been tested up to that speed and might work at higher
speeds).

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