pjh@mccc.uucp (Pete Holsberg) (11/12/90)
The question came up recently as to whether or not a math coprocessor would be a useful addition to a UNIX computer system. One of us said that it would not unless the programs that were being run used floating point and/or extended integer arithmetic. The other said that one will find relatively few programs which do not do at least SOME floating point or extended integer math, even if it is not explicitly present in the program it may be present in a library routine. Inquiring minds would like to know who is closest to the truth. Let us limit the discussion to UNIX systems running with CPUs that do not have math coprocessors built-in, if you don't mind. Thanks, Pete -- Prof. Peter J. Holsberg Mercer County Community College Voice: 609-586-4800 Engineering Technology, Computers and Math UUCP:...!princeton!mccc!pjh 1200 Old Trenton Road, Trenton, NJ 08690 Internet: pjh@mccc.edu Trenton Computer Festival -- 4/20-21/91
gwyn@smoke.brl.mil (Doug Gwyn) (11/12/90)
In article <1990Nov12.032526.17125@mccc.uucp> pjh@mccc.uucp (Pete Holsberg) writes: >The question came up recently as to whether or not a math coprocessor >would be a useful addition to a UNIX computer system. One of us said >that it would not unless the programs that were being run used floating >point and/or extended integer arithmetic. The other said that one will >find relatively few programs which do not do at least SOME floating >point or extended integer math, even if it is not explicitly present in >the program it may be present in a library routine. If the math coprocessor runs asynchronously, the kernel may require some subtle hackery to properly context switch. I ran into this when adapting Sixth Edition UNIX for use on a PDP-11/34 with FPU. (Fortunately, for the most part I was able to borrow the FPU support code from the PDP-11/45 version.) Even with math coprocessor hardware, you still need for the compilers to generate floating-point instructions. Most often they will simply generate calls to run-time library arithmetic support routines, which are implemented using the basic integer instruction set. Then, you need to be aware that any code that uses FP instructions and is copied to a system that does not have the FP hardware is going to generate exceptions; whether or not the kernel attempts to emulate the FP operations or simple posts a SIGFPE to the process, the results will be rather miserable. As to how much FP hardware will help a typical application, the answer is that it of course depends on the application. Most "system" software will be essentially unaffected by the availability of FP hardware. A few engineering-style, and some graphics, applications can speed up noticably using FP hardware. I would say that unless you have identified a particular bottleneck application that heavily uses floating point, you'd be wasting your money to buy an FPP.
pb@uucp (Peter Brouwer) (11/13/90)
In article <1990Nov12.032526.17125@mccc.uucp> pjh@mccc.uucp (Pete Holsberg) writes: >The question came up recently as to whether or not a math coprocessor >would be a useful addition to a UNIX computer system. One of us said >that it would not unless the programs that were being run used floating >point and/or extended integer arithmetic. The other said that one will >find relatively few programs which do not do at least SOME floating >point or extended integer math, even if it is not explicitly present in >the program it may be present in a library routine. Awk uses floatig point a lot. I think most programs don't use float arithmetic. If your source does not contain float or double type variables ( or not in hot places ) your not using float arithmatic. I think there are not many C library functions who are using float arithmetic. -- # Peter Brouwer, | Philips Information Systems, # # NET : pb@idca.tds.philips.nl | Department P9000-i Building V2, # # UUCP : ....!mcsun!philapd!pb | P.O.Box 245,7300AE Apeldoorn,The Netherlands# # PHONE:ext [+31] [0]55 432992, | FAX :ext [+31] [0]55 433488 #
lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall) (11/14/90)
In article <1007@apdnm.idca.tds.philips.nl> pb@idca.tds.philips.nl (Peter Brouwer) writes:
: Awk uses floatig point a lot. I think most programs don't use float arithmetic.
Perl uses floating point a lot too.
Larry Wall
lwall@jpl-devvax.jpl.nasa.govalan@mq.com (Alan H. Mintz) (11/14/90)
In article <1990Nov12.032526.17125@mccc.uucp>, pjh@mccc.uucp (Pete Holsberg) writes: > The question came up recently as to whether or not a math coprocessor > would be a useful addition to a UNIX computer system. One of us said > that it would not unless the programs that were being run used floating > point and/or extended integer arithmetic. The other said that one will > find relatively few programs which do not do at least SOME floating > point or extended integer math, even if it is not explicitly present in > the program it may be present in a library routine. The SCO XENIX 386 O/S definitely makes use of the FPU if it is available (according to SCO). I'll try and run some benchmarks with/without in a couple days, but it definitely "feels" faster. Most SCO applications will use FPU's also. Some Foxbase+ results: Task time/without time/with Video Speed 20 20 Tight Loop 52 20 File Creation 26 20 Small Record Processing 77 20 Large Record Processing 64 20 Text Export/Import 20 20 Simple Math 48 20 Complex Math 176 20 -- < Alan H. Mintz | Voice +1 714 980 1034 > < Micro-Quick Systems, Inc. | FAX +1 714 944 3995 > < 10384 Hillside Road | ...!uunet!mq!alan > < Alta Loma, CA 91701 USA | alan@MQ.COM >
seanf@sco.COM (Sean Fagan) (11/15/90)
In article <10349@jpl-devvax.JPL.NASA.GOV> lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall) writes: >Perl uses floating point a lot too. So, Larry, when are you going to write you FP-emulator in perl? Is that going to be before or after the OS in perl? -- -----------------+ Sean Eric Fagan | "*Never* knock on Death's door: ring the bell and seanf@sco.COM | run away! Death hates that!" uunet!sco!seanf | -- Dr. Mike Stratford (Matt Frewer, "Doctor, Doctor") (408) 458-1422 | Any opinions expressed are my own, not my employers'.
seanf@sco.COM (Sean Fagan) (11/15/90)
In article <126@mq.com> alan@mq.com (Alan H. Mintz) writes: >The SCO XENIX 386 O/S definitely makes use of the FPU if it is available >(according to SCO). The kernel does not use floating point. All SCO systems (for the '286 and later) can assume that there is a subset of an 8087 available, as we ship an FP emulator with the OS. (The reason the kernel doesn't use floating point is because, if there were no FPU present, bad things would happen during the trap to the emulator.) -- -----------------+ Sean Eric Fagan | "*Never* knock on Death's door: ring the bell and seanf@sco.COM | run away! Death hates that!" uunet!sco!seanf | -- Dr. Mike Stratford (Matt Frewer, "Doctor, Doctor") (408) 458-1422 | Any opinions expressed are my own, not my employers'.
pjh@mccc.uucp (Pete Holsberg) (11/16/90)
In article <126@mq.com> alan@mq.com (Alan H. Mintz) writes:
=The SCO XENIX 386 O/S definitely makes use of the FPU if it is available
=(according to SCO).
Do they say in what way the OS uses it?
=I'll try and run some benchmarks with/without in a couple
=days, but it definitely "feels" faster.
I'd love to see the results.
=
=Most SCO applications will use FPU's also. Some Foxbase+ results:
=
=Task time/without time/with
=
=Video Speed 20 20
=Tight Loop 52 20
=File Creation 26 20
=Small Record Processing 77 20
=Large Record Processing 64 20
=Text Export/Import 20 20
=Simple Math 48 20
=Complex Math 176 20
That column of 20s makes me sceptical!
Pete
--
Prof. Peter J. Holsberg Mercer County Community College
Voice: 609-586-4800 Engineering Technology, Computers and Math
UUCP:...!princeton!mccc!pjh 1200 Old Trenton Road, Trenton, NJ 08690
Internet: pjh@mccc.edu Trenton Computer Festival -- 4/20-21/91paulz@sco.COM (W. Paul Zola) (11/20/90)
In article <1990Nov15.184607.21575@mccc.uucp> pjh@mccc.edu (Pete Holsberg) writes: >In article <126@mq.com> alan@mq.com (Alan H. Mintz) writes: >=The SCO XENIX 386 O/S definitely makes use of the FPU if it is available >=(according to SCO). > > Do they say in what way the OS uses it? > [deleted] There has been a great deal of confusion about this. To put it as clearly as possible: the SCO XENIX *kernel* and the SCO UNIX *kernel* do NOT use floating-point calculations. Since they don't use floating-point calculations, they don't use the FPU, even if one is present. What the SCO kernels do provide is a means by which application programs can use the FPU if one is present. The access to the FPU is transparent to the application: applications always "see" an FPU present, and always use the FPU instructions. It is the kernel's job to hand off the FP instructions to the co-processor chip (if one is present) or to emulate the FP instruction (if there is no FPU present or if the kernel was instructed to ignore the FPU via the 'ignorefpu' boot string directive). In summary: If an application uses floating-point instructions and an FPU is present, then the kernel will make sure the application uses the FPU. If an application uses floating-point instructions and an FPU is not present, then the kernel will emulate the FPU on behalf of the application. In no case does the kernel itself use floating-point instructions or the FPU. I hope this clarifies things for people. - Paul Zola Software Support Engineer paulz@sco.COM We only know in theory what we are doing. - Kate Bush DISCLAIMER: I speak for myself, and not for SCO.
gordon@sneaky.UUCP (Gordon Burditt) (11/27/90)
> If an application uses floating-point instructions and an FPU > is present, then the kernel will make sure the application > uses the FPU. > If an application uses floating-point instructions and an FPU > is not present, then the kernel will emulate the FPU on behalf > of the application. > In no case does the kernel itself use floating-point instructions > or the FPU. How, then, is it arranged that process A and process B, both of which use floating point, don't stomp all over each other's FPU registers? It would seem that the kernel must minimally load and unload the FPU state when necessary due to process switches between processes using the FPU. If it doesn't use any floating-point instructions, how does it figure out whether the FPU is present? Gordon L. Burditt sneaky.lonestar.org!gordon
lws@comm.wang.com (Lyle Seaman) (12/12/90)
gordon@sneaky.UUCP (Gordon Burditt) writes: >How, then, is it arranged that process A and process B, both of which use >floating point, don't stomp all over each other's FPU registers? It would >seem that the kernel must minimally load and unload the FPU state when >necessary due to process switches between processes using the FPU. It's probably because the kernel is non-preemptable, so the FP operation runs to completion before the process switch. >If it doesn't use any floating-point instructions, how does it figure out >whether the FPU is present? Does it matter? -- Lyle Wang lws@comm.wang.com 508 967 2322 Lowell, MA, USA uunet!comm.wang.com!lws The scum always rises to the top.