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Re: APIC: what is it good for? Can I switch it off?


Stefan Gößling-Reisemann (<debian-user@lists.debian.org>) wrote:

> I am trying to find the reason for our fileserver to shutdown
> unexpectedly (and without any warning entries in the logs). I have
> come across a warning during bootup:
> "Spurious 8259A interrupt: IRQ7"
> As a consequence (??) the ERR field in /proc/interrupts increases
> steadily (by an amount of about 60 per hour).
> What does that mean? Is there a hardware glitch??
> After some Google'ing I found that "Spurious ..."  seems to be a
> warning which might be related to APIC and IO-APIC being activated in
> the kernel-config. As one source mentioned, the APIC is for
> communication of CPU in SMP-machines. We only have one CPU, so can I
> safely switch it off in the config?

IO-APIC can be used on single processor machines to get more than 16

  0:   32809327    IO-APIC-edge  timer
  1:      14220    IO-APIC-edge  i8042
  4:     631691    IO-APIC-edge  serial
  5:          0   IO-APIC-level  uhci_hcd, uhci_hcd, uhci_hcd
  7:          2    IO-APIC-edge  parport0
  8:          1    IO-APIC-edge  rtc
  9:          0   IO-APIC-level  acpi
 12:     171457    IO-APIC-edge  i8042
 14:      66254    IO-APIC-edge  ide0
 15:         92    IO-APIC-edge  ide1
 16:    2863271   IO-APIC-level  nvidia
 17:          0   IO-APIC-level  eth0
 18:      27558   IO-APIC-level  EMU10K1
 19:          4   IO-APIC-level  bttv0, Bt87x audio

This will however only work if the mainboards it.

> On another note: what would be the difference to disabling it via
> "noapic" appended to the boot command? Does that do the same trick?

It should do the same. By the way, you tan switch off the local IO apic
only using the "nolapic" parameter.

best regards
 Andreas Janssen

Andreas Janssen <andreas.janssen@bigfoot.com>
PGP-Key-ID: 0xDC801674 ICQ #17079270
Registered Linux User #267976

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