Thread View: comp.sys.ibm.pc.rt
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Started by Steve Dyer
Sun, 23 Jul 1989 18:21
AFPA performance
Author: Steve Dyer
Date: Sun, 23 Jul 1989 18:21
Date: Sun, 23 Jul 1989 18:21
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I'd like to get a feeling for the magnitude of floating point performance increase by adding the AFPA board to a model 125 running the Sep or Dec 88 release of AOS 4.3. I also understand that there are TWO AFPA boards for sale now, one of which was designed for and shipped with the model 125, and one which is shipped with the 130 and 135 (but can be used with the 125, if my understanding is correct.) Is there any reason NOT to buy the newer AFPA board? I believe their prices are similar.
Re: AFPA performance
Author: William L. Moran Jr.
Date: Mon, 24 Jul 1989 06:58
Date: Mon, 24 Jul 1989 06:58
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In article <12926@bloom-beacon.MIT.EDU> dyer@arktouros.mit.edu (Steve Dyer) writes: >I'd like to get a feeling for the magnitude of floating point >performance increase by adding the AFPA board to a model 125 >running the Sep or Dec 88 release of AOS 4.3. > I hate to say this, but my experience is that the eafpa (enhanced advanced ... :) is not a real big win over the regular 125 - mc68881 I've seldom seen performance more than 20% better on pure floating point stuff on a 135 with eafpa vs. 125 with no fpa just a mc881. I suspect this may have something to do with the compiler as I've heard that AIX does much better than this. Anyway, rumors I've heard say that for AOS, the afpa may actually do worse than the mc881, although I don't have an afpa to test this with. Bill Moran -- arpa: moran-william@cs.yale.edu or wlm@ibm.com uucp: uunet!bywater!acheron!archet!wlm or decvax!yale!moran-william ------------------------------------------------------------------------------- Well, I guess if I had to swear one way or another, I'd say he wasn't insane - he just had strange rhythms. Hunter S. Thompson
Re: AFPA performance
Author: Larry Breed
Date: Wed, 09 Aug 1989 04:05
Date: Wed, 09 Aug 1989 04:05
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In article <263@archet.UUCP> wlm@archet.UUCP (William L. Moran Jr.) writes: > >I hate to say this, but my experience is that the eafpa (enhanced >advanced ... :) is not a real big win over the regular 125 - mc68881 >I've seldom seen performance more than 20% better on pure floating >point stuff on a 135 with eafpa vs. 125 with no fpa just a mc881. I >suspect this may have something to do with the compiler as I've heard >that AIX does much better than this. Anyway, rumors I've heard say >that for AOS, the afpa may actually do worse than the mc881, although >I don't have an afpa to test this with. > > Bill Moran You're probably not seeing the best floating point performance AOS offers. The default floating-point code generated by pcc, hc, f77, and hf77 uses the run-time floating linkage (RTFL) so that objects will run on whatever floating hardware is installed. Code tailored for the run-time hardware is generated in data storage the first time a given fp operation is executed. The code is pretty good but can't match the performance of inline code. Only hf77 can generate inline code for the AFPA. Try compiling with the -f2 option, and measure that performance. Larry Breed
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