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1E

Category: BIOS

INT 1E - SYSTEM DATA - DISKETTE PARAMETERS

Notes:	the default parameter table (see #01264) is located at F000h:EFC7h for
	  100% compatible BIOSes
	if the table is changed, INT 13/AH=00h should be called to ensure that
	  the floppy-disk controller is appropriately reprogrammed
	before rebooting the machine, this pointer should be restored to point
	  to the original position of the floppy parameters in the ROM BIOS.
	  The DOS boot sector takes care of this and in the case of a bootstrap
	  error, resets the vector. It also passes the original pointer to the
	  IO.SYS/IBMDOS.COM file for possible later restoration.
	under PhysTechSoft's PTS ROM-DOS this table is fictitious.
	the DR-DOS multi-OS LOADER (at least 1.04 up to including DR-DOS 7.03)
	  does not alter the INT 1Eh vector when launching IBMBIO.COM files
	  via its boot methods "S" or "D".  Although this allows booting
	  (uncompressed) IBMBIO.COM files bigger than 29 KB, it may
	  occasionally cause the floppy parameters to get trashed due to a 
	  bug in the DR-DOS 7.03 IBMBIO.COM startup code.
BUG:	The 2nd level decompressor of the DR-DOS 7.03 IBMBIO.COM (1998/08/11 to
	  1999/07) start-up code erroneously assumes that the floppy parameters
	  reside at 0000h:7C00h (normally set up there by the boot sector)
	  instead of relying on the INT 1Eh vector to point at their location.
	  Since the "assumed" floppy parameters get moved around and INT 1Eh
	  gets updated to point to their new location, this may cause the
	  contents of the floppy params to get trashed, if they weren't
	  actually copied to 0000h:7C00h by the bootstrap loader (that is the
	  boot sector or the LOADER utility).
SeeAlso: INT 13/AH=0Fh,INT 41"HARD DISK 0",INT 4D/AH=0Ah


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