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Date:      Fri, 14 May 2004 11:17:18 -0700 (PDT)
From:      Matthew Dillon <dillon@apollo.backplane.com>
To:        John Baldwin <jhb@freebsd.org>
Cc:        Android66 <android.66@volja.net>
Subject:   Re: BTX halted
Message-ID:  <200405141817.i4EIHIsH031735@apollo.backplane.com>
References:  <40A3C047.80804@volja.net> <200405131550.28566.jhb@FreeBSD.org> <40A49439.9080409@volja.net> <200405141138.09168.jhb@FreeBSD.org>

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:>
:> BTW, if it's not a bother, what does the code below actually do? I don't
:> speak asm so I can't tell what are the bad things that my BIOS does :)
:
:It tries to see if it is running in protected mode with paging enabled so it 
:can walk the page tables to extract physical addresses for its DMA.  The vm86 
:monitor that our boot code uses doesn't let the BIOS read the page table 
:pointer register (%cr3) so it blows up.
:
:-- 
:John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
:"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org
    
    I wonder if this is related to random BTX faults I get on my
    Athlon 64 3200+ boxes.  We're using the 5.x boot loader for DFly.

    Most of the time the boot loader is able to load and boot the kernel,
    but about 20% of the time (more if I don't have a keyboard plugged in)
    it fails with a BTX fault in random places, before it even gets to
    the menu.  It's very non-deterministic.  Most of the time its fine,
    some times it fails on cold boot, sometimes it fails after a reset
    button boot, sometimes it fails after a 'reboot'.

    Once the kernel is running everything always works dandy, and it
    happens to both of my Shuttle (FN85 MB) boxes, but never on my tower
    (K8V MB) box, so I am positive it isn't a hardware issue.

						-Matt



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