AH = 07 AL = interleave value (XT only) BX = format buffer, size = 512 bytes; the first 2*(sectors/track) bytes contain F, N for each sector where: F = 00h for good sector F = 80h for bad sector N = sector number on return: AH = status (see INT 13,STATUS) CF = 0 if successful = 1 if error - BIOS disk write attempts should reset the controller on error - only the disk number is checked for validity