I am experiencing the similar problem on my Acer Aspire 5000 laptop -
once in a while a bunch of "APIC error on CPU0: 40(40)" messages are
showing up in dmesg.

After few experiments and a lot of googling, I identified a cause - it
was my built-in wireless card! Disabling IO-APIC helped, besides a
single "Spurious 8259A interrupt: IRQ7" message while booting up there
was nothing unusual.

A did some further experiments on various hardware and from my
experience I can tell that "APIC error" messages are entirely hardware
related.

Regards,
Konstantin

On Sat, 2007-07-14 at 08:09 -0400, Justin Piszcz wrote:
quoted text
> I have an older MSI motherboard and when I enable the following option:
> 
> >From lshw:
>         description: Motherboard
>         product: MS-6730
> 
> [*]   IO-APIC support on uniprocessors
> 
> I get the following errors in dmesg:
> 
> [  247.177372] APIC error on CPU0: 00(40)
> [  247.556741] APIC error on CPU0: 40(40)
> [  262.010412] APIC error on CPU0: 40(40)
> [  262.765553] APIC error on CPU0: 40(40)
> [  263.876481] APIC error on CPU0: 40(40)
> [  264.191962] APIC error on CPU0: 40(40)
> [  265.040566] APIC error on CPU0: 40(40)
> [  267.959689] APIC error on CPU0: 40(40)
> [  269.446029] APIC error on CPU0: 40(40)
> [  269.853344] APIC error on CPU0: 40(40)
> [  271.122825] APIC error on CPU0: 40(40)
> [  271.287051] APIC error on CPU0: 40(40)
> [  273.825237] APIC error on CPU0: 40(40)
> [  274.373737] APIC error on CPU0: 40(40)
> [  275.355775] APIC error on CPU0: 40(40)
> [  275.982087] APIC error on CPU0: 40(40)
> [  276.101181] APIC error on CPU0: 40(40)
> [  276.173611] APIC error on CPU0: 40(40)
> [  276.970970] APIC error on CPU0: 40(40)
> [  277.561575] APIC error on CPU0: 40(40)
> [  278.694486] APIC error on CPU0: 40(40)
> [  279.353573] APIC error on CPU0: 40(40)
> [  281.779398] APIC error on CPU0: 40(40)
> [  283.625457] APIC error on CPU0: 40(40)
> [  284.749322] APIC error on CPU0: 40(40)
> [  284.983013] APIC error on CPU0: 40(40)
> [  285.126394] APIC error on CPU0: 40(40)
> 
> I normally do not use this option (which also gets rid of the errors*1), 
> but I am curious, why do these errors occur?  I remember them with the early
> 2.6.x series and they are still re-occurring in 2.6.22.1.
> 
> The weird part-- is when IO-APIC is disabled, I see this on boot:
> 
> IO-APIC DISABLED:
> 
> [   46.902712] XFS mounting filesystem md0
> [   47.017322] spurious 8259A interrupt: IRQ7.
> [   47.273009] Ending clean XFS mount for filesystem: md0
> 
> IO-APIC ENABLED:
> 
> [   46.851012] XFS mounting filesystem md0
> [   47.103066] Ending clean XFS mount for filesystem: md0
> 
> * 1 Anytime I see a spurious interrupt on (usually older hardware) 
> especially during file I/O this usually means corruption (from what I 
> have seen) that is why I don't really want to trust anything on this host.
> 
> Anyone have any idea what's going on here?
> 
> Justin.
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