INT 13 - DISK - WRITE DISK SECTOR(S)
        AH = 03h
        AL = number of sectors to write (must be nonzero)
        CH = low eight bits of cylinder number
        CL = sector number 1-63 (bits 0-5)
             high two bits of cylinder (bits 6-7, hard disk only)
        DH = head number
        DL = drive number (bit 7 set for hard disk)
        ES:BX -> data buffer
Return: CF set on error
        CF clear if successful
        AH = status (see AH=01h)
        AL = number of sectors transferred
Notes:  errors on a floppy may be due to the motor failing to spin up quickly
          enough; the write should be retried at least three times, resetting
          the disk with AH=00h between attempts
        the IBM AT BIOS and many other BIOSes use only the low four bits of
          DH (head number) since the WD-1003 controller which is the standard
          AT controller (and the controller that IDE emulates) only supports
          16 heads
        AWARD AT BIOS and AMI 386sx BIOS have been extended to handle more
          than 1024 cylinders by placing bits 10 and 11 of the cylinder number
          into bits 6 and 7 of DH
SeeAlso: AH=02h,AH=0Bh

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