HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens

                        INT 13,4 - Verify Disk Sectors

       AH = 04
       AL = number of sectors to verify  (1-128 dec.)
       CH = track/cylinder number  (0-1023 dec., see below)
       CL = sector number  (1-17 dec.)
       DH = head number  (0-15 dec.)
       DL = drive number (0=A:, 1=2nd floppy, 80h=drive 0, 81h=drive 1)
       ES:BX = pointer to buffer

       on return:
       AH = status  (see INT 13,STATUS)
       AL = number of sectors verified
       CF = 0 if successful
          = 1 if error


       - BIOS disk reads should be retried at least three times and the
         controller should be reset upon error detection
       - causes controller to calculate the CRC of the disk data and
         compare it against the CRC stored in the sector header
       - BIOS before 11/15/85 required ES:BX point to a valid buffer
         that doesn't cross DMA boundaries.   More recent BIOS versions
         actually ignore the buffer and the DMA boundary requirement
       - use this function to check for valid formatted diskette in a
         the specified drive and for drive ready for read
       - only the disk number is checked for validity
       - the parameters in CX change depending on the number of cylinders;
         the track/cylinder number is a 10 bit value taken from the 2 high
         order bits of CL and the 8 bits in CH (low order 8 bits of track):

         │F│E│D│C│B│A│9│8│7│6│5-0│  CX
          │ │ │ │ │ │ │ │ │ │  └─────  sector number
          │ │ │ │ │ │ │ │ └─┴───────  high order 2 bits of track/cylinder
          └─┴─┴─┴─┴─┴─┴─┴──────────  low order 8 bits of track/cyl number

       - see   DETECTING

Esc or Alt-X to exit int 13,4 Home/PgUp/PgDn/End ←↑↓→