Datasheet

Command Processing
2-34 C141-C008
(2) Alternate area
The alternate area in user space (spare sectors within each cell and alternate cells)
are excluded from the abovementioned logical data block addresses. Access to
allocated sectors as alternate blocks within the alternate area is performed
automatically by the IDD’s defect management (sector slip processing and
alternate block processing), so it is not particularly necessary for the user to
access the alternate area. Also, data blocks in the alternate area cannot be clearly
specified and accessed directly.
2.8.3 Variable TPI/BPI
The IDD selects a possible combination of TPI (tracks per inch) types per head
and BPI types per head × zone from the following ranges:
TPI: Seven types within a range defined by the maximum value - 20%
BPI: Eight types within a range defined by the standard value ±10%
Up to four TPI types can be selected in a single device. Only the required BPI
types can be selected (determined by factory settings).
Accordingly, in an area in which TPI and BPI differ, the number of cylinders in
the user space, the number of cylinders in a cell, and the number of sectors in a
track vary according to the head.
Basic device capacity:
The basic capacity of a device is defined as its maximum TPI - 3.3% (29
cylinders per cell) + standard BPI. This basic device capacity is guaranteed for
any combination of TPI and BPI.
Basic device performance:
The performance of a device is defined as its maximum TPI (30 cylinders per
cell) + standard - 3.3% BPI. Devices with other combinations of TPI and BPI
also satisfy this basic performance value.