Int 13h, 1Ah            Format ESDI Unit                                 PS/2

    Formats IBM ESDI Fixed Disks.

        Entry   AH = 1Ah
                AL = Relative Block Address (RBA) defect table block count
                          = 0 → No RBA table
                          > 0 → RBA table used
                ES:BX = Address of RBA table
                CL = Modifier bits:
                          Bit 7   Must be 0
                          Bit 6   Must be 0
                          Bit 5   Must be 0
                          Bit 4   1 → Perform periodic interrupt
                                      (interrupt formatting
                                      after every cylinder so
                                      host program can show
                                      formatting progress)
                          Bit 3 = 1 → Perform extended surface
                                      analysis
                          Bit 2 = 1 → Update secondary defect map
                          Bit 1 = 1 → Ignore secondary defect map
                          Bit 0 = 1 → Ignore primary defect map
                DL = Drive Number (Bit 7 = 1 for hard disks)

    ──────────────────────────────────────────────────────────────────

    This service is for formatting high-capacity PS/2 hard disks. The
    software for this process is provided in the ESDI adapter for
    these disks. You have the option of requesting automatic
    interruptions after every cylinder is formatted (which means your
    program can list the cylinder number currently being formatted).

    Note
    This format may take more than an hour to complete, and is usually
    only performed by operating system software.