Format of disk address packet:
Offset	Size	Description	)
 00h	BYTE	size of packet (10h or 18h)
 01h	BYTE	reserved (0)
 02h	WORD	number of blocks to transfer (max 007Fh for Phoenix EDD)
 04h	DWORD	-> transfer buffer
 08h	QWORD	starting absolute block number
		(for non-LBA devices, compute as
		  (Cylinder*NumHeads + SelectedHead) * SectorPerTrack +
		  SelectedSector - 1
 10h	QWORD	(EDD-3.0, optional) 64-bit flat address of transfer buffer;
		  used if DWORD at 04h is FFFFh:FFFFh