Maxtor D540X-4G - Manual (Page 15)

Product Description
Maxtor D540X-4G 2-3
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The Logical Block Address (LBA) mode can only be utilized in systems that support
this form of translation. The cylinder, head and sector geometry of the drive, as
presented to the host, differs from the actual physical geometry. The host AT
computer may access a drive of set parameters: number of cylinders, heads and
sectors per track, plus cylinder, head and sector addresses. However, the drive can’t
use these host parameters directly because of zoned recording techniques. The drive
translates the host parameters to a set of logical internal addresses for data access.
The host drive geometry parameters are mapped into an LBA based on this formula:
LBA = (HSCA - 1) + HHDA x HSPT + HNHD x HSPT x HCYA
= (HSCA - 1) + HSPT x (HHDA + HNHD x HCYA)
where HSCA = Host Sector Address, HHDA = Host Head Address
HCYA = Host Cylinder Address, HNHD = Host Number of Heads
HSPT = Host Sectors per Track
The LBA is checked for violating the drive capacity. If it does not, the LBA is
converted to physical drive cylinder, head and sector values. The physical address is
then used to access or store the data on the disk and for other drive related
operations.
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Each drive model has a fixed number of spare sectors per drive, all of which are
located at the end of the drive. Upon detection of a bad sector that has been
reassigned, the next sequential sector is used.
For example, if sector 3 is flagged, data that would have been stored there is “pushed
down” and recorded in sector 4. Sector 4 then effectively becomes sector 3, as
sequential sectors are “pushed down” across the entire drive. The first spare sector
makes up for the loss of sector 3, and so maintains the sequential order of data. This
push down method assures maximum performance.
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Immediately following power down, dynamic braking of the spinning disks delays
momentarily allowing the read/write heads to move to an inner mechanical stop. A
small fixed magnet holds the rotary actuator in place as the disk spins down. The
rotary actuator is released only when power is again applied.