1 Scope

This technical report assumes that the reader is familiar with the conventional Int 13h interface, the usage of the Device Parameter Table, and the basic operation of ATA devices. This technical report describes in detail extensions to the BIOS and extensions to the data maintained by the BIOS.

The disk-drive industry has increased the capacity and functionality of the ATA-compatible disk drive, finally surpassing the capability of some BlOSs to service these new capabilities. This specification addresses the following BIOS specific problems:

- The BIOS must support drives with a capacity greater than 528 MB. The conventional Int 13h interface has a limit of 1024 cylinders;

- The Int 13h interface allows more than two drives to be attached to a system but has no consistent method for storing the additional parameters;

- CHS-independent methods for accessing the drives have now been defined. These are drive-geometry independent and require a different method of address representation and operation;

- New methods of data transfer continue to be added to ATA devices. Capabilities such as, DMA modes, multi-sector data transfers and Fast PIO are not reported to the operating system;

- Systems require more than two disk drives, and with this requirement comes the requirement to assign the order in which the drives are to be accessed.