Intel 386 manual Coprocessor .HARDWARE Interface

COPROCESSOR .HARDWARE INTERFACE

606b/a7/6MlSb MACRO		ASSEMBLER	Test for presence of a Numerics Chip,						Revision 1.0	PAGE 2
LOC	OBJ	LINE	SOURCE
001F	'BD'Ea	~,		fld1				Must use default control word froIR FNINIT
0022	'BD'EE	50		fldz				Form	infinity	,
0025	'BDEF'	51		fdiv				6067/267 says. inf = -inf
0026	'BD'C0	52		fld		st		Form	negative infinity
002B	'BD'E0	53		fchs				i387 SX/DX NPX says .inf <> -inf
002E	'BDED'	5~		fcompp				See	if they are the salle and reRlQve them
0031	'BDD3C	55		fstsw		{sO·		Look	at status from	FCOMPP
003~	6B0~	5b		lIIav		ax,[siJ		See if the infinities matched
003b	'E	57		sahf
0037	7~0b	56		je		found_a7_2a7		Jump	if a0a7l287 is	present
		5'		An i367 SX/DX NPX is present', If denormal exceptions are used for an 6B.!.71267,
		b0
		b1		they	must be masked. The i367 SX/DX NPX will automatically normalize denormal
		b2		operands faster than an exception handler can·
003'	EB07'0	b3		jmp		found_3a7 SLDX
		b~
003C		b5		set	up	f or	no NPX
		bb
		b7
		b6		jmp	exi t
003C	EB0~'0	b'
003F		70	found_8L287:
		71		set	up	for	8712a7
		72
003F	EB01'0	73			exit
		7~		jllP
00~2		75	found-3a7 :
		76		set up for 367 SLDX
		77
		76	~xit:
00~2		7'		ends
		a0	code
		a1		end		start I ds: dgroup I ss: dgroup: ~st

ASSEMBLY COMPLETE, NO ERRORS FOUND

Figure 5-3. Software Routine to Recognize the Coprocessor (Contd.)

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