Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hpcvlx!kcl
From: kcl@hpcvlx.HP.COM (Ken C. Lo)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Testing for a numeric coprocessor
Message-ID: <101000054@hpcvlx.HP.COM>
Date: 29 Jun 89 16:35:52 GMT
References: <2584@blake.acs.washington.edu>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 22


   There is a FNINIT instruction the 80286 can execute to determine
   whether or not the 80287 is presented.

   FND_287: FNINIT                          ;initialize Numerical Processor
            FSTSW AX                        ;retrieve 80287 status word
            OR    AL,AL                     ;test low byte of 80287's
                                            ;exception flags
                                            ;if all zero,then 80287 is present
                                            ;and properly initialized
                                            ;if not all zero, then 80287 absent
            JZ    GOT_287                   ;branch if 80287 present

            SMSW  AX                        ;No Numerical Processor
            OR    04H                       ;set EM bit in machine status
                                            ;word
            LMSW  AX                        ;enable software emulation of 80287


   GOT_287  SMSW  AX                        ;Numerical processor present
            OR 02H                          ;set MP bit in machine status word
            LMSW  AX                        ;permit normal 80287 operation