9 Aug
2013
9 Aug
'13
6:48 p.m.
On Aug 9, 2013 6:38 PM, "Chuck Guzis" <cclist at sydex.com> wrote:
Write precompensation [... is] usually done with MFM,
because MFM is
somewhat more susceptible to timing jitter, but there's no reason
that it
couldn't be used on, say, GCR as well.
In fact, it was nearky always done with GCR on hard drives, though the GCR
was usually more specifically known as (1,7) RLL or (2,7) RLL. Both codes
would be unusable at normal flux densities on hard drives.
It typically wasn't done with GCR on 5.25 inch floppies because the schemes
in use (e.g., by Apple and Commodore) weren' t using flux density as high
as the standard MFM format. (I'm not sure about the GCR on rt he Victor
9000.)
Eric