I used to use run-length limited codes also in the disk biz also. A further
advance in detection technology came about starting about 5 years ago with
partial response channels. One is called "PRML" which stands for "partial
response, maximum liklihood". We liked to call it "Partially right, mostly
lucky" instead.... but I digress.
Even Crystal oscillator frequencies change with temperature. They go up
when it gets hotter, down when it gets colder. Also, propagation delays
through electronics change with temperature; bipolar gets faster, MOS get's
slower. So, when it's 50 degrees in the morning and a car posts a .00x and
then later in the afternoon when it's 80 degrees that same car can run the
same time but it's a .00y, that's y.
BTW, drives have become a commodity... kind of like table salt. When I
started in the drive business 25 years ago capacity cost over $500,000 a
Megabyte, now it costs less than 1/2 a cent per Megabyte.
-- Rick
> Rick, Please tell us about why the JAC timer is not accurate to .001 of a
> second.
>
> Long ago our EE guy, Bob McCullouch (spelling?) by name, praised the value
> of a crystal oscillator to ensure accuracy.
>
> Is the third digit at random?
>
> McCulloch, a founding partner in a Silicon Valley electronic biz,
> 20 years ago started his own business manufacturing hard drives capable of
> storing massive amounts of memory for the time. He used a system called
> "Run Length Limited" which was originally developed by IBM for main frames.
> About a year later Apple and others routinely installed hard drives with
> even more memory.
>
> Somebody has a McCulloch timer in the corner of his garage. He
> built several units in conjunction with Terry McHenry who is now racing a
> Huffaker-built Fiero in SFR races.
>
> --John Kelly
>
>
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