8.1. Geometry translation
In a DOS environment host adapter option ROM's are required to support the logical block addressing as defined by the INT 13h Extensions document. For backward compatibility, SCSI option ROM's are required to support the current INT 13h functions as well. To determine the geometry for INT 13h function 08h, these option ROM's read the partition table from the disk at LBA 0 and if it exists as determined by the 55AAh signature at offset 1FEh, use the existing geometry to calculate the Cylinder-Head-Sector (CHS) values. Appendix A provides an example of how to determine the geometry. If the partition table does not exist, SCSI option ROM's may use any algorithm to set the CHS values.