A computer process establishes data frequencies for recording data in
zones of a zone bit recording medium in a disc drive. At least three data
points are identified for each zone correlating data frequencies and
corresponding bit error rates, and a slope of a curve between each two
data points is calculated. The slopes are averaged, and the data
frequency is calculated based on the average slope. If a difference
between the average and default slopes exceeds a first threshold value,
or if a spread of the slopes exceeds a second threshold value, the data
frequency is calculated based on the average slope and the default slope.
In one embodiment, each of the three data points is generated by
recording data in the zone at each of three selected data frequencies,
reading the recorded data, and calculating bit error rates based on the
recorded and read data.