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Date:      08 Apr 95 13:47:56+0200
From:      "Georg-W. Koltermann" <gwk@racer.dkrz.d400.de>
To:        bugs@FreeBSD.org
Subject:   80387 hangs system at divide by zero
Message-ID:  <9504081147.AA03909@racer.dkrz.de>

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Hi,

I am having a problem on my system with post 2.0 snapshots (some
snapshot in January and now 950210-SNAP).  My system hangs in the npx
probe routine during bootup.  Only the reset switch can wake it up
again.  I inserted printf's in the code and could isolate the place:
it hangs where the driver forces a divide by zero in order to learn
which type of exception reporting the hardware uses.  The system boots
up normally when I either boot the kernel with the -c option and
'disable npx0' (that's what I usually do so that I can work at all) or
when I skip the divide by zero code in the npx driver, hard coding
IRQ13 exception reporting at that point.  In the latter case the
system will hang when I later start a program which divides by zero.

The 2.0-RELEASE didn't hang during boot, but I assume it also hung
when I divided by zero in a program.  At least I could force a lock up
by starting any X11 application with a -fontname string which
contained a pixel size of zero.  xfontsel would also lock up the
system while scanning the fonts right after popping up it's main
window.

Did you know about this problem?  Is IRQ13 exception reporting broken
in the current versions?

I have a 40 MHz Intel 80386 noname system with a ULSI '387.  This
problem is not too darn important to me, I can currently live with
disabling the '387, and hopefully I can upgrade to some sort of '486
later this year...   :-)  ...just thought you might be interested.  If
you want me to try anything specific just let me know.

Georg.

P.S.: Thanks for your work!  This is a great system!




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