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 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