Note: This API call is for DOS personality only. Use Family API for portability.
Int 21H, AH=53H
2 and higher
TRANSLATE BIOS PARAMETER BLOCK TO DRIVE PARAM BLOCK
AH = 53h DS:SI -> BIOS Parameter Block (see #01663) ES:BP -> buffer for Drive Parameter Block (see #01395 at AH=32h) DBP drive byte must be set to valid drive (Windows95-OSR2) ---Windows95--- CX = signature 4558h ('EX') for FAT32 extended BPB/DPB (see #01664) DX = signature 4152h ('AR') for FAT32 extended BPB/DPB
ES:BP buffer filled
for DOS 3.0+, the cluster at which to start searching is set to 0000h and the number of free clusters is set to FFFFh (unknown) if the number of sectors per cluster is set to zero, MS-DOS will hang at startup because it computes the internally-used shift count by shifting this value right until the carry flag is set; since this will never happen when the field is zero, MS-DOS hangs not supported by Windows NT 3.1
Text based on Ralf Brown Interrupt List Release 61