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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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