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T13/2132-D Revision 3 June 23, 2010
42 Working Draft Enhanced Disk Drive - 4 (EDD-4)
8.14 Check Extensions Present (FN 41h)
This function shall be used to check for the presence of INT 13h extensions. If CF=1b, the extensions are not
supported for the requested device. If CF=0b, BX shall be checked to confirm that it contains the value AA55h
indicating that the extensions are present. If BX = AA55h, the value of CX shall be checked to determine what
subsets of this interface are supported for the requested device. At least one subset shall be supported. The
version of the extensions shall be 30h. This indicates that the INT 13h extensions are compliant with this
standard.
Entry
AH 41h
BX 55AAh
DL BIOS device number
Exit
Carry Clear Function completed without error
AH Version of extensions. Shall be set to 30h
AL Vendor Specific
BX AA55h
CX Interface support bit map (see table 21)
Carry Set Function completed with an error
AH Shall be set to the error code 01h (Invalid Command)
Table 21 — Interface Support Bit Map
Bit Description
0 If the content of this bit is one, then the Fixed disk access subset shall be supported.
1 If the content of this bit is one, then the Device locking and ejecting subset shall be supported.
2 This bit shall be set to one to indicate that the Enhanced disk drive support subset is present.
3 If the content of this bit is one, then the 64-bit extensions are present. When the 64-bit extensions
are present, the fields starting at offset 10h in the Device Address Packet are valid.
15:4 Reserved.