and less than
50ppm drift. The typical system was usually within
50ppm of exact and drifted less than 25ppm over temperature extremes.
Often the actual data rate was far lower than that reference(usually 1/4
or 1/8th).
IMHO it's very misleading - or even worse, foolish - to worry about errors in
the ppm range when the instantaneous rotation speed of the floppy can
vary a few percent.
Exactly the point. ;)
Whatever the clock error may be it's trivial and stable compared to the
mechanical system and the magnetics.
Look up "PRML" or "Partial Response
Maximum Likelihood". It's a
branch of signal decoding for use in situations where adjacent pulses
most definitely have measureable effects on each other.
Understood, I was trying to stay out of the land of obscure terms
and letters.
MFM, M2FM, RLL
or GCR), and previous bits history it should be
straightforward enough to predict the likely next transistion(s)
be they one or zero.
Most uses of PRML look both forward *and* backwards.
Very true, the 765, 1793 and their heirs select precomp on a bit level for
this on the write case to make the read case easier.
Allison