Int 13/AH=42h

IBM/MS INT 13 Extensions - EXTENDED READ

AH = 42h
DL = drive number
DS:SI -> disk address packet (see #00272)

Return:
CF clear if successful
AH = 00h
CF set on error
AH = error code (see #00234)
disk address packet's block count field set to number of blocks
successfully transferred

See Also: AH=02h - AH=41h"INT 13 Ext" - AH=43h"INT 13 Ext"


Format of disk address packet:

Offset  Size    Description     (Table 00272)
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

Category: Disk I/O Enhancements - Int 13h - I

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