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; By: Jeffrey Nonken
page 60,132
.286
_text segment byte public 'code'
_text ends
_data segment word public 'data'
_data ends
const segment word public 'const'
const ends
_bss segment word public 'bss'
_bss ends
dgroup group const, _bss, _data
assume cs: _text, ds: nothing
_data segment word public 'data'
even
env_8087 dw 47 dup (?)
norm_8087 dw 177fh
_data ends
_text segment byte public 'code'
;
; This code saves the 80x87 enviroment and sets up our own. First, this
; assumes you are running an 80287; the 8087 may require more FWAIT
; operations. Second, I decided that I didn't want to handle exceptions, so
; I simply disabled them. That means that if the 80x87 gets an invalid result
; (such as divide-by-zero) the 80x87 will continue to run and will produce
; invalid results until the end of your current calculation. Anything that
; depends on the results will, of course, also be invalid. If you want
; exceptions to be handled, get documentation for the 80x87 and you will
; see how to set norm_8087 (above) to suit your needs. If you are running
; an 8087 and don't know where to put FWAIT instructions, you can always
; add one after each floating-point instruction. NOTE: FWAIT is synonymous
; to WAIT. They are the same instruction.
;
; This was written for TURBO C and will also work with MSC. It should work
; with any programming language with no more than minor changes in the
; label names or the interface. Consult your compiler manual for more detail.
; I wrote this so it would work with either the tiny or small models.
; Actually, it will probably work with any of the models. You should be
; able to assemble this with MASM and link it right in.
;
; extern save_8087();
; extern restore_8087();
;
public _save_8087
_save_8087 proc near
cli ; no interruptions!
lea bx,dgroup:env_8087 ; point to save area
fwait ; make sure processor is ready
fnsave [bx] ; save the 8087 environment
lea bx,dgroup:norm_8087 ; point to our new 8087 setup
mov ax,[bx] ; get it
fldcw [bx] ; set it
fwait
sti ; restore interrupts
ret
_save_8087 endp
public _restore_8087
_restore_8087 proc near
cli ; no interruptions!
lea bx,dgroup:env_8087 ; point to saved 8087 stuff
frstor [bx] ; restore the 8087 environment
sti ; restore interrupts
ret
_restore_8087 endp
_text ends
end
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