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Date:      Mon, 29 Sep 1997 21:01:08 -0700 (PDT)
From:      Tom <tom@sdf.com>
To:        Tony Kimball <Anthony.Kimball@East.Sun.COM>
Cc:        michaelv@MindBender.serv.net, freebsd-chat@freefall.freebsd.org
Subject:   Re: supermicro p6sns/p6sas 
Message-ID:  <Pine.BSF.3.95q.970929205250.5247A-100000@misery.sdf.com>
In-Reply-To: <199709291920.OAA25886@compound.east.sun.com>

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On Mon, 29 Sep 1997, Tony Kimball wrote:

> Quoth Tom on Mon, 29 September:
> : 
> :   The Pentium division bug was fixed long ago.  And Intel gave free
> : replacements to everyone.
> 
> Yes.  Similarly, by all reports, the K6 bug is fixed, and free
> replacements are available.  I have to wonder whether Intel would have
> offered the free replacements if the division bug had not been so well
> publicized, but can only speculate and/or compare past vendor
> behaviour.

  Yes, but you have to apply for each replacement.  Replacements for
known broken versions are not automatic.

> :   What?  The "make world" problems were VERY serious.  Simple operations
> : in gcc were being preformed incorrectly sometimes, causing core dumps.
> : Such failures appeared in all kinds of other software as well.
> 
> Well, not all kinds.  I understand that the various flavors of Windows
> are not known to demonstrate the bug.  Seriousness in real-world terms

  I don't know about that.  Application errors and GPFs are much more
common on K6 CPUs, from experience.  Why?  I can't say.  But the fact that
gcc dumps core randomly on the same CPU makes wonder if it the same
problem.  Win95 hardly provides detailed error reports.

> means loss of life/limb/property.  Wasted time is one form of partial
> loss of life, and certainly having to type 'make world' again is a
> waste of time, but a floating-point error in an embedded system could

  Waste of time?  A little more than that.  A make world would NOT EVER
complete on such a CPU.  DG has demonstrated this bug, and described it to
the list.  He has a K6 that will not complete a make world ever.  At the
time, he could not even return it.

> crash your airliner or slam your missile into a hospital.  Again,
> relatively weighting the seriousness of the bugs in practice, I'd have
> to say that the major losses incurred in each case were those of the
> manufacturer.  Certainly Intel lost more money on the division bug,
> but then they made more on the sales in the first place.  The whole
> issue seems pretty subjective/hypothetical: No actual airliners ever
> used a pentium in a critical component to my knowledge, or if they did

  Hmmm, I remember a componet of flight control gear on a boeing airliner
used Intel CPUs.  I think they could have still been using 486 processors,
because the design lead period was so long.  This was a while back.  I
read it in a design case study in a journal somewhere.

Tom




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