Xref: utzoo comp.sys.att:4636 unix-pc.general:1584 Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!labrea!rutgers!gatech!ncar!boulder!pikes!csm9a!isis!scicom!zebra!vern From: vern@zebra.UUCP (Vernon C. Hoxie) Newsgroups: comp.sys.att,unix-pc.general Subject: Re: FPU on the UNIX pc Keywords: math library, compiler, MC68881 Message-ID: <126@zebra.UUCP> Date: 24 Oct 88 06:55:21 GMT Article-I.D.: zebra.126 References: <368@uncle.UUCP> <3462@rphroy.UUCP> <528@icus.islp.ny.us> Organization: Alpha Science Computer Networks, Denver, Colo. Lines: 39 In article <528@icus.islp.ny.us>, lenny@icus.islp.ny.us (Lenny Tropiano) writes: > In article <3462@rphroy.UUCP> tkacik@rphroy.UUCP (Tom Tkacik) writes: > |>In article <368@uncle.UUCP> jbm@uncle.UUCP (John B. Milton) writes: > |> > |>The software will be the tricky part. First the math libraries will need to > |>be re-written, and made compatible with the existing ones. > > I'm not to sure about this, but reading the UNIX System V User's Manual > (vol. II) on cc(1), I saw this: > > "The C compiler uses one of three code generators for the > > CPU=xxxxx,FPU=yyyyy The Motorola Manual for the 68010 gives the following: "Word patterns with bits 12-15 equaling 1010 or 1111 are distinguished as unimplemented instructions and separate exception vectors are given to these patterns to permit efficient emulation. This facility allows the operating system to detect program errors, or to emulate unimplemented instructions, such as the MC68881 Floating Point Coprocessor instructions, in software." The idea was that if a co-processor is on board, the control is handed over to it, otherwise the Supervisor mode will process the data in software. Now the question is: Did ATT/Convergent implement the software with this in mind? or did they put all the options control in the compiler? If they built the software as Motorola designed the chip, the FPU instructions were used and trapped to software emulation. The object code produced would then work whether the machine had an FPU or not. It would just run slower if not. This is going to take some reverse engineering with a dis-assembler if someone at ATT doesn't come up with a definitive answer. -- Vernon C. Hoxie {ncar,nbires,boulder,isis}!scicom!zebra!vern 3975 W. 29th Ave. voice: 303-477-1780 Denver, Colo., 80212 uucp: 303-455-2670