Intel 80286, 80287 manual SYSTEM-LEVEL Numeric Programming, Software Routine to Recognize

SYSTEM-LEVEL NUMERIC PROGRAMMING

8086/87/88/186 MACRO ASSEMBLER		Test for presence of 8 Nuner;cs Chip, Revision 1.0	PAGE
DOS 3.20 (033·N) 8086/87/88/186 MACRO ASSEMBLER V2.0 ASSEMBLY OF MOOULE TEST_NPX
OBJECT MOOULE PLACEO IN FINDNPX.OBJ
LOC OBJ	LINE	SOURCE

1 +1 Stitle('Test for presence of a Nuner;cs Chip, Revision 1.0 1 )

2

3

name

Test_NPX

4

0000

(100

5

stack

segment

stack

I stack I

6

dw

100 dup (1)

1??7

)

00C8

?171

7

sst

dw

8

stack

ends

9

0000

0000

10

data

segment

publ ie

'datal

11

t"""

dw

Oh

12

data

ends

13

14

dsroup

group

data,

stack

15

cgroup

group

code

16

17

code

segment

publ ic

'code'

18

assune

cs:cgroup, ds:dgroup

19

0000

20

start:

21

22

Look for

an 8087.

80287.

or 80387 NPX.

23

Note that we cannot execute \lA1T on 8086/88 if no 8087 is present.

0000

24

25

test_npx:

0000 900BE3

26

tninit

; Must use non-wait form

0003

BEOOOO

27

moy

si ,offset

dgroup:tefl1J

0006 C7045A5A

28

mov

word

ptr

[si] ,SASAH ;

Initial ize

tenp to non-zero value

OOOA 90003C

29

fnstsw

[si]

; Must use non-wait form of fstsw

30

It is not necessary to -use a WAIT instruction

0000

803COO

31

after

fnstsw

or fnstew.

00 not use one here.

32

cnp

byte

ptr

[si] ,0

; See

if

correct

status with zeroes was read

0010 752A

33

jne

no_npx

; JUTp if not a

val id status

word, meaning no NPX

34

		35
		36
		37
		38
0015	8804	39
0017 253Fl0		40
001A	303FOO	41
0010	751D	42
		43
		44

45

46

47

48

Now see if ones can be correctly written from the control word.

fnstcw	[si]	;	Look at the control word; do not use \iAIT form
	ax, [si]	; Do not use a \iAIT instruction here!
moy		;	See if ones can be written by NPX
and	aX,10lfh	;	See if selected parts of control word look OK
c""	aX,lfh	i	Check that ones and zeroes were correct l y read
jne	no_npx	; Jurp if no NPX ;s installed

Some rn.merics chip h installed. NPX instructions and \iAIT are now safe. See if the NPX·is an 8087, 80287, or 80387.

This code is necessary if a denormal exception handler is used or the new 80387 instructions wi II be used.

001F	9809E8	49	fldl		; Must use default control word from fNINIT
0022	9B09EE	50	fld.		;	form infinity
0025	9BOEF9	51	fdiv		;	8087/287 says +fnf II • inf
0028	9B09CO	52	fld	st	;	Form negative Infinity
0028	9BD9EO	53	fchs		;	80387 says +Inf <> • inf
DD2E	9BDED9	54	fconw		i	See if they are the same and remove them
0031	9BD03C	55	fstSN	[si]	i	Look at status from FCOMPP
OD34	8B04	56	IIIOY	ax, [sf]
0036	9E	57	sahf			See if the infinities matched
0037	7406	58	je	fOAJnd_87_287	;	J"", if 8087/287 is present
		59

Figure 3-1. Software Routine to Recognize the 80287

3-3