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    Subjectunexpected IRQ trap at vector ac (kernel oddity)
    Has anyone come across the 'unexpected IRQ trap at vector ac' error ? I've
    been very perplexed by this issue. At present I'm running a crippled SMP
    setup. It appears that I may have a corrupted MP Table.

    I can boot the system if I disable MP table / APIC from the BIOS.
    The problem is that I am forced to use a UP instead of SMP setup.
    Not a very desireable situation.

    I have a fairly robust ASUS A7m266 mboard. The symptoms occured
    immediately after I added an additional 512MB SDRAM PC3100, giving me 1GB
    total phys RAM.

    System specs :

    Dual Athlon XP 2.4Ghz CPUs
    1GB RAM PC3100
    GeForce2 Ti4200 graphics Card
    Slack 10.1 ( kernel

    Error rec'd:
    Total 2 processors activited bogomips (7913.47)
    checking 2 TSC synchro acros 2CPU passed
    Brought up 2CPUs
    Unexpected IRQ trap at vector AC
    PCI BIOS revision 2.0 entry at
    PCI using config type 1
    mtrr: v2.0 (20020519)
    mtrr: your CPUs had inconsistent fixed MTRR settings probably your BIOS
    does not setup all CPUS

    Unexpected IRQ trap at vector ab

    What I've done to BIOS as work arounds:

    1) shut of CPU1/CPU2 cache
    2) disabled power mgmt
    3) disabled APIC
    4) disabled MP table (forced box to run w/one CPU -not desireable)

    modified '/etc/lilo.conf'

    append="hdc=ide-cd pci=noacpi acpi=off"

    None of the above actions solved the problem of the system booting with
    one CPU only. When I setup BIOS defaults the system hangs as described

    So more recently, I update the kernel from 2.6.10 to To no
    avail the issue is unchanged.

    I'm thinking that I may have to reflash the BIOS, not easy to do when you
    run exclusively LINUX. I suppose I could boot the machine w/an XP CD, and
    then flash the BIOS.

    Any thoughts? Has anyone witnessed and solved this issue ?
    Thx in advance for the help.



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