🚀 go-pugleaf

In article <1256@hoptoad.uucp> gnu@hoptoad.uucp (John Gilmore) writes:
[Discussing clocking data faster on the outside tracks of a disk]
>
>I don't know how to figure it out exactly, but I suspect that this
>simple change (to a disk and its controller) could double the amount of
>stuff you could put on the same disk with the same heads and almost the
>same electronics.

The problem is that it ISN'T a simple change.  You have to design a circuit
which can handle extreme variations in input data at a fairly high frequency.
While circuits like this can be designed, they are neither simple nor cheap.

Illustrative example: assume an 8" disk, first track at 7", last at 3.5".
Obviously, the data on the 7" track will be recorded at twice the clock
frequency, since the track is exactly twice as long as the first.  If we
assume 5MHz data rate on the 3.5" track, this is a 5MHz data rate at the
7" track; any circuit designed to handle both will be considerably more
complex than one designed only to handle one (and remember, the circuit
must also handle all in-between cases too!).  Even more importantly, one of
the most critical of circuit elements in a disk controller is the timing
circuitry, which must be highly accurate in order to "catch" the bits
properly.  Designing a circuit of sufficient accuracy which would operate
over an (at least) two-to-one range is VERY difficult.


-- 
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                 "... if the church put in half the time on covetousness
Mike Farren      that it does on lust, this would be a better world ..."
hoptoad!farren       Garrison Keillor, "Lake Wobegon Days"