INT 80 - AMI BIOS v1.00.12.AX1T - internal - BIOS SUBSYSTEM SELECTION

	AH = function
	    00h install and initialize BIOS subsystem
		AL = ??? (00h,01h,03h)
		CX:BX = subsystem ID (see #03971)
		ESI = address from which to load, or 00000000h for default for
			subsystem
		EDI = physical address at which to install, or 0 for default
		Note:	if CX=0000h on entry, this call is applied to all
			  subsystems whose ID has low word BX
	    01h get BIOS subsystem information
		CX:BX = subsystem ID (see #03971)
		Return: AL = ???
			AH = ???
			EDX = uncompressed size of subsystem in bytes
			SI = offset within subsystem of initialization
				routine, or FFFFh if none
			EDI = physical address of default location or 0
	    02h get matching subsystem identifier
		AL = index into subsystem list (return ALth occurrence
		      matching BX)
		BX = low word of subsystem identifier
			(0001h,0002h,0004h,0005h,000Bh,FFFFh)
		Return: CF clear if successful
			    CX = high word of ALth matching subsystem
			CF set on error
		Note:	the system is halted if AL=00h on entry
	    03h set up "big real" mode (4G segment limits)
	    04h turn off "big real" mode (restore 64K segment limits)
	    05h remove BIOS subsystem
		CX:BX = subsystem ID to leave out
		Note:	the system is halted if an invalid (not installed)
			  subsystem ID is specified
	    06h get installed subsystem info
		CX:BX = subsystem ID (see #03971)
		Return:	CF clear
			EDX = length of ???
			EDI = linear address of start of ???
		Note:	the system is halted if an invalid (not installed)
			  subsystem ID is specified
Return: CF clear if successful
	CF set on non-fatal error
Note:	this interrupt vector is cleared to 0000h:0000h near the end of the
	  BIOS startup sequence