INT 25 - DOS 1+ - ABSOLUTE DISK READ (except partitions > 32M)
AL = drive number (00h = A:, 01h = B:, etc)
CX = number of sectors to read
DX = starting logical sector number (0000h - highest sector on drive)
DS:BX -> buffer for data
Return: CF clear if successful
CF set on error
AH = status
80h device failed to respond (timeout)
40h seek operation failed
20h controller failed
10h data error (bad CRC)
08h DMA failure
04h requested sector not found
03h write-protected disk (INT 26 only)
02h bad address mark
01h bad command
AL = error code (same as passed to INT 24 in DI)
may destroy all other registers except segment registers
Notes:  original flags are left on stack, and must be popped by caller
this call bypasses the DOS filesystem
BUG:    DOS 3.1 through 3.3 set the word at ES:[BP+1Eh] to FFFFh if AL is an
invalid drive number
SeeAlso: INT 26

See also: 1302

25 - DOS 1+ - ABSOLUTE DISK READ (except partitions > 32M)