Specifications
AMD Geode™ GeodeROM Functional Specification 51
Non-Removable Media
32087C
6.2.7 Function 09h - Set Drive Parameters
Description:
Initializes the fixed disk controller with the parameters that correspond to the installed drive. The intent of this function
was originally to allow a plug-in ISA drive controller to service many different types of drives. Since IDE drives have an
integrated controller, this function is theoretically no longer necessary, as the controller is specifically designed to sup-
port the geometry of the drive it is physically attached to. However, many drive controllers still require that the BIOS
issue this interrupt during POST.
Supports:
Fixed disk only.
Passed:
Returns:
Special Instructions:
The vectors at 0:[41h*4] (INT 41h) and 0:[46h*4] (INT 46h) point to the parameter tables for drives 80h (C:) and 81h
(D:), respectively. Issuing INT 13h Function 09h with DL = 80h or 81h causes the BIOS to download those parameters
pointed to by the corresponding vector to the drive’s controller. In a four-drive system, there are no such interrupt vec-
tors, and the actual location of the parameter tables for drives 82h (E:) and 83h (F:) are unknown to the caller.
Traditionally, fixed disks have a “native” cylinder/head/sector count. Ideally, it is these values that are used by the BIOS
to initialize the drive during POST. This guarantees the drive’s interpretation of the caller’s CHS values during a Read/
Write/Verify operation are always correct. Some drives behave poorly when initialized with non-native parameters and
map sectors.
Related Functions:
None.
Parameter Description
AH 09h
DL Drive number
Parameter Description
CF 0 = Success
1 = Failure
AH Status code: See AH in "Function 01h - Get Disk Subsystem Status" on page 46