INT 13 - ESDI FIXED DISK - FORMAT UNIT (PS)
        AH = 1Ah
        AL = defect table count
        CL = format modifiers (see below)
        DL = drive
        ES:BX -> defect table
Return: CF set on error
        AH = status (see AH=01h)
Note:   if periodic interrupt selected, INT 15/AH=0Fh is called after each
          cylinder is formatted
SeeAlso: AH=07h,INT 15/AH=0Fh

Bitfields for format modifiers:
 bit 4  generate periodic interrupt
 bit 3  perform surface analysis
 bit 2  update secondary defect map
 bit 1  ignore secondary defect map
 bit 0  ignore primary defect map

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