INT 2F - CD-ROM - ABSOLUTE DISK READ
        AX = 1508h
        ES:BX -> buffer
        CX = drive number (0=A:)
        SI:DI = starting sector number
        DX = number of sectors to read
Return: CF set on error
            AL = error code (15=invalid drive,21=not ready)
        CF clear if successful
SeeAlso: AX=1509h

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