IBM IC25N040ATCS04 Hard Drive Specifications - Page 108
Address Offset Feature vendor specific, 11.1 Enable/Disable Address Offset Mode
View all IBM IC25N040ATCS04 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 108 highlights
11.11 Address Offset Feature (vendor specific) 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 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. The Set Max pointer is set to the end of the reserved area to protect the data in the user area when operating in offset mode. This protection can be removed by a Set Max Address command to move the Set Max pointer to the end of the drive. But any commands which access sectors across the original native maximum LBA are rejected with error, even if this protection is removed by a Set Max Address command. 11.11.1 Enable/Disable Address Offset Mode Subcommand code 09h Enable Address Offset Mode offsets address Cylinder 0, Head 0, Sector 1, LBA 0, to the start of the nonvolatile 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 the Read Max Address command allows access to the entire drive. Addresses wrap so the entire drive remains addressable. If a nonvolatile 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 nonvolatile Set Max Address command. Before Enable Address Offset Mode A reserved area has been created using a non-volatile Set Max command. User Accessible Area Reserved Area LBA 0 LBA R LBA M After Enable Address Offset Mode The former reserved area is now the user accessible area. The former user accessible area is now the reserved area. User Accessible Area (former Reserved Area) Reserved Area (former User Accessible Area) LBA 0 LBA M-R LBA M After Set Max Address Command useing the Value Returned by Read Max Address LBA 0 User Accessible Area LBA M Figure 70. Device address map before and after Set Feature Travelstar 60GH & 40GN hard disk drive specifications 95