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Newsgroups: comp.unix.bsd Path: sserve!manuel.anu.edu.au!munnari.oz.au!metro!ipso!runxtsa!bde From: bde@runx.oz.au (Bruce Evans) Subject: Re: [386bsd] installing fpu (ULSI) results in floating exceptions Message-ID: <1992Dec1.175549.19319@runx.oz.au> Organization: RUNX Un*x Timeshare. Sydney, Australia. References: <1992Nov30.013413.1119@ponds.uucp> <1992Nov30.060552.7912@kithrup.COM> <ByJIpL.69w@unx.sas.com> Date: Tue, 1 Dec 92 17:55:49 GMT Lines: 20 In article <ByJIpL.69w@unx.sas.com> sastdr@torpid.unx.sas.com (Thomas David Rivers) writes: > That is, we all _know_ that the '387 is a superset of the '287, and > that '287 instructions should work with a '387; but ULSI didn't know > that... Their chip only implements the strictly '387 instructions. > (I don't know what these strictly '387 instructions are, what is/isn't > implemented... seems strange to me.) Um, the 387 (or at least the 486) is _not_ a superset of the 287. It lacks at least the FPSETPM instruction. Big deal. In addition, the i486 manual takes 8 pages to describe all the small differences between an 8087-287 and an 387-486. The 287 had many minor deficiencies. The differences should not cause any problems with the default 386BSD setup. But don't expect to run your hand-crafted IEEE-conformant 387 code on a 287. I suspect that the problems are caused by hardware differences and bugs in the 386BSD exception handlers. -- Bruce Evans (bde@runx.oz.au)