An apparatus and method for selecting physical cylinders (cylinders accessible
for read/write operations) in a disc drive is provided. The disc drive includes
at least one rotatable disc. The disc drive also includes a first head, which is
positionable adjacent a first disc surface, and a second head, which is positionable
adjacent a second disc surface. The first disc surface has a first plurality of
greycode tracks and the second disc surface has a second plurality of greycode
tracks. Each greycode track of the second plurality of greycode tracks corresponds
to a different greycode track of the first plurality of greycode tracks, thereby
forming a plurality of greycode cylinders, with each greycode cylinder of the plurality
of greycode cylinders including a pair of corresponding greycode tracks. The physical
cylinders are a subset (less than all) of the plurality of the greycode cylinders.
The method of selecting the physical cylinders includes determining whether the
first plurality of greycode tracks or the second plurality of greycode tracks demonstrates
greater track eccentricity, to thereby obtain a maximum track eccentricity surface
and a corresponding maximum eccentricity head. The maximum track eccentricity surface
is one of the first and second disc surfaces and the maximum eccentricity head
is a corresponding one of the first and second heads. The maximum eccentricity
head is used to locate at least one of the physical cylinders.