INT 41H and INT 46H: Hard Disk Parameter Pointers

 These vectors (0:0104 and 0:0118) are pointers to hard disk operating

 parameter structures on AT-class and better computers.



 See Hard Disk Parameter Table for a layout of the data at these vectors.



 XT: Depending upon switch settings, one of four addresses are copied to

 these vectors.



 AT: At Boot time, the AT BIOS reads the CMOS Memory to learn which type(s)

 of hard disk drives are attached.  It then points the vectors...



     INT 41H  --> first hard disk

     INT 46H  --> second hard disk



 ...to tables in ROM.  Many recent BIOSes are able to handle "user-defined"

 hard-disk types.  They store the necessary parameters in non-volatile RAM

 and copy them into memory at boot time.



See Also: BIOS Data Area

          ROM-BIOS Functions

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