Path: utzoo!utgpu!watserv1!watmath!att!att!linac!uwm.edu!zaphod.mps.ohio-state.edu!usc!apple!mips!winchester!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: 386 Clones [really: IEEE floating point & various approaches; long] Message-ID: <42677@mips.mips.COM> Date: 3 Nov 90 01:37:21 GMT References: <1990Oct26.015244.586@amd.com> <8464@scolex.sco.COM> <42618@mips.mips.COM> <4186@goanna.cs.rmit.oz.au> Sender: news@mips.COM Reply-To: mash@mips.COM (John Mashey) Organization: MIPS Computer Systems, Inc. Lines: 33 In article <4186@goanna.cs.rmit.oz.au> ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes: >It's worth pointing out that SIGFPE does not meet the IEEE criteria. >SIGFPE is a blanket "some kind of floating point exception, or maybe >some kind of integer exception, _I_ know but I'm not going to tell _you_". >(That is, according to SVID 2. I don't know what SVr4 does. 4.xBSD >does have the courtesy to tell you what kind of exception you got.) >The IEEE standard calls for *separate* enabling and disabling of each >of the five traps, with separate handlers of the user's choice for each. >I'm going to cite the SVID rather than 1003.1, and that's for two reasons. >First, my copy of 1003.1 is in another city and I don't remember exactly >what it says. Second, the degree to which the RS/6000 behaviour has >something to do with the degree to which you have been able to rely on >SIGFPE in the past, and 1003.1 is not the past. The SVID says that 1) SVID, to be honest, was fairly irrelevant to this, in that it described an interface, but gave as a future direction IEEE exception-handling. (note, of course, that FP was not exactly a major concern of that issue of the SVID, and I'd certainly guess that the bulk of the UNIX-based FP computing has been done on BSD-derived OSs, or merged variants.) 2) People who've built IEEE-based computers who worried about FP have long ago included some approximation or other to full IEEE-signal handlers. I'm sure Sun did; we did, and I'd assume others did also. Maybe somebody from Sun & HP would say what they do. We of course let you turn on/off specific traps, and when you get a SIGFPE, there's a field to tell you which one it was. -- -john mashey DISCLAIMER: UUCP: mash@mips.com OR {ames,decwrl,prls,pyramid}!mips!mash DDD: 408-524-7015, 524-8253 or (main number) 408-720-1700 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086