INT 13 - HARD DISK - PS/1 and newer PS/2 - READ MULTIPLE DISK SECTORS

	AH = 21h
	AL = number of sectors to write
	CH = low byte of 12-bit cylinder number
	CL = starting sector (bits 0-5) and bits 8-9 of cylinder (bits 6-7)
	DH = head number (bits 0-5) and bits 10-11 of cylinder (bits 6-7)
	DL = drive number (80h,81h)
	ES:BX -> buffer for data to be read
Return: CF clear if successful
	    ES:BX buffer filled
	CF set on error
	AH = status (see #00234 at AH=01h)
Desc:	read from the disk using the Multiple Block mode available on newer
	  IDE drives and some hard disk controllers, which generates an
	  interrupt only after the end of transferring a group of sectors
	  rather than after each sector
Notes:	must call AH=24h"PS/1" before using this function
	input values in CL and DH are not range-checked
	the byte at address 0040h:0074h is set to the status of the operation
SeeAlso: AH=02h,AH=22h"PS/1",AH=23h"PS/1",AH=24h"PS/1"