The table below shows how the three translation modes compare. This is done by showing
a summary of the different modes used in the overall path from the operating system,
through the BIOS, to the hard disk controller, to the physical drive platters:
Interface |
Standard CHS |
Extended CHS (ECHS) /
Large |
Logical Block
Addressing |
Physical Drive
Platters to Integrated Disk Controller |
Physical Geometry |
Physical Geometry |
Physical Geometry |
Integrated Disk
Controller to BIOS |
Logical Geometry |
Logical Geometry |
Logical Block Address |
BIOS to Operating
System and Applications (through Int 13h) |
Logical Geometry |
Translated Geometry |
Translated Geometry |
Notice how in all three schemes the physical geometry is hidden within the hard disk
itself. In the case of LBA, the logical geometry is presented to the BIOS only so it can
be translated for use by the operating system; communication between the BIOS and the hard
disk controller occur using the logical block address.
For modern drives that use Int13h extensions, only logical block addressing is used.
Next: Caveats on Changing Translation Modes and Transferring Hard Disks Between PCs
