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AH = 05h AL = interleave value (XT-type controllers only) ES:BX -> 512-byte format buffer the first 2*(sectors/track) bytes contain F,N for each sector F = sector type 00h for good sector 20h to unassign from alternate location 40h to assign to alternate location 80h for bad sector N = sector number CH = cylinder number (bits 8,9 in high bits of CL) CL = high bits of cylinder number (bits 7,6) DH = head DL = drive
Return:
CF set on error CF clear if successful AH = status code (see #00234)
Notes: 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. For XT-type controllers on an AT or higher, AH=0Fh should be called first. 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. Not all controller support sector types 20h and 40h. Under Windows95, an application must issue a physical volume lock on the drive via INT 21/AX=440Dh before it can successfully write to the disk with this function
See Also: AH=05h"FLOPPY" - AH=06h"FIXED" - AH=07h"FIXED" -
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