SPI Tolerance

Jeff Stai stai at dt.wdc.com
Fri May 27 16:45:53 PDT 1994

Hi Bill...

I always read it as an absolute limit. In other words, if you say 100,
then it is 100.0000000.... etc. It cannot be less than or equal to
99.99999999.....etc. What I mean is, 100 means anywhere between 100 and
an infinitessimal below 104. 96 means between 96 and and an
infinitessimal below 100.

If you can't guarantee that you will never go below 100, then you must
negotiate at 96. By specifying a tolerance, you've only moved the
problem in the general case; i.e., if I say "100 +/- 0.25", then if I
still might drop below 99.75000....etc., I still must choose 96. Only
the threshold has moved.

In your specific case, a tolerance let's you go ping your drive vendor,
I'll grant you that. But, no fair changing the rules in the middle of
the game!-)

Does this make sense?

jeff stai
western digital I/O products
stai at dt.wdc.com

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