Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!jarthur!nntp-server.caltech.edu!madler
From: madler@nntp-server.caltech.edu (Mark Adler)
Newsgroups: comp.sys.next
Subject: Re: cc compiler problems
Summary: it's an fpu emulation code bug fixed in 2.1
Message-ID: <1991Apr9.051123.8923@nntp-server.caltech.edu>
Date: 9 Apr 91 05:11:23 GMT
References: <9104090229.AA27828@nextasy2.eecs.wsu.edu>
Organization: California Institute of Technology, Pasadena
Lines: 29

In article <9104090229.AA27828@nextasy2.eecs.wsu.edu> dwatola@NEXTASY2.EECS.WSU.EDU (David Watola) writes:
>this point has been raised more than once, and has not been satisfactorily 
>addressed.  i have looked at the optimized assembly code, and it looks fine.

(This is in reference to the short code segment discovered by Bing Chen
that kills 68040 NeXT's in a major way ...)

I had someone at NeXT try that program on a 68040 running version 2.1 of
the operating system (with -O), and it did not crash the machine.  I will
verify this when I get my 2.1 upgrade.  The reason 2.1 might be expected
to fix this is that 2.1 has new fpu emulation code from Motorola that
fixes several bugs in the emulation that comes with 2.0.  NeXT mentions
two of those, the slow floor() and incorrect tanh() functions, in the
2.1 "fixed" list.  They are careful not to mention the much more serious
total machine obliteration on intensive numerical computation bug that
is manifested in the tight divide loop of that program.  NeXT also says
that not all 2.0 users need to upgrade to 2.1.  An unsupportable statement
given this very serious bug which renders any 68040 NeXT a computer that
is unable to compute (under 2.0).  As in previous postings, I cannot
recommend strongly enough that 68040 users should upgrade to 2.1.  However
you can get it is legal, so long as you are already running 2.0 (there is
no license fee to go from 2.0 to 2.1).

I suspect that one of the reasons NeXT has this odd attitude about 2.0
is that there is no satisfactory means for OD-only 68040-upgraded cubes
to get the 2.1 update.  This is just specualtion though ...

Mark Adler
madler@pooh.caltech.edu