Address Offset Feature; Enable/Disable Address Offset Mode - Hitachi HDS725050KLA360 Specifications

10.15 Address Offset Feature

Computer systems perform initial code loading (booting) by reading from a predefined address on a disk drive. To
allow an alternate bootable operating system to exist in a system reserved area on a disk drive this feature provides
a Set Features function to temporarily offset the drive address space. The offset address space wraps around so that
the entire disk drive address space remains addressable in offset mode. Max LBA in offset mode is set to the end of
the system reserved area to protect the data in the user area when operating in offset mode. The Max LBA can be
changed by an Set Max Address command to access the But any commands which access sectors across the original
native maximum LBA are rejected with error, even if this protection is removed by an Set Max Address
command.5.15.1 Enable/Disable Address Offset Mode
Set Features subcommand code 09h Enable Address Offset Mode offsets address Cylinder 0, Head 0, Sector 1, LBA
0, to the start of the non-volatile protected area established using the Set Max Address command. The offset
condition is cleared by Subcommand 89h Disable Address Offset Mode, Hardware reset or Power on Reset. If
Reverting to Power on Defaults has been enabled by Set Features command, it is cleared by Soft reset as well. Upon
entering offset mode the capacity of the drive returned in the Identify Device data is the size of the former protected
area. A subsequent Set Max Address command with the address returned by Read Max Address command allows
access to the entire drive. Addresses wrap so the entire drive remains addressable.
If a non-volatile protected area has not been established before the device receives a Set Features Enable Address
Offset Mode command, the command fails with Abort error status.
Disable Address Offset Feature removes the address offset and sets the size of the drive reported by the Identify
Device command back to the size specified in the last non-volatile Set Max Address command.

10.15.1 Enable/Disable Address Offset Mode

Set Features subcommand code 09h Enable Address Offset Mode offsets address Cylinder 0, Head 0, Sector 1, LBA
0, to the start of the non-volatile protected area established using the Set Max Address command. The offset
condition is cleared by Subcommand 89h Disable Address Offset Mode, Hardware reset or Power on Reset. If
Reverting to Power on Defaults has been enabled by Set Features command, it is cleared by Soft reset as well. Upon
entering offset mode the capacity of the drive returned in the Identify Device data is the size of the former protected
area. A subsequent Set Max Address command with the address returned by Read Max Address command allows
access to the entire drive. Addresses wrap so the entire drive remains addressable.
If a non-volatile protected area has not been established before the device receives a Set Features.
Deskstar 7K500 and Deskstar E7K500 Hard Disk Drive Specification
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