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Old 02-03-2011, 02:03 AM   #1
kenneho
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Registered: May 2003
Location: Oslo, Norway
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MP-BIOS bug: 8254 timer not connected to IO-APIC


Hi all,


The "MP-BIOS bug: 8254 timer not connected to IO-APIC" error message
shows up on boot on at least one of my RHEL servers, and I'm not quite
sure what to make of it. My understanding of the situation is that the
timer is located elsewhere on the motherboard than where the kernel
looks for it. Is this correct?

I've come across people suggestin one should disable APIC by adding
"noapic" to the kernel boot options, but which consequences does this
imply - in SNP setups only one CPU will be used by the kernel?

Best regards,
kenneho

PS. I posted this question on a RHEL mailing list, but since I didn't get any replies I'm posting it here too.
 
Old 02-03-2011, 03:46 PM   #2
H_TeXMeX_H
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I've gotten this message before, and sometimes it correlates with problems, and other times it doesn't. Does it cause problems ? If not, ignore it.

If it causes problems, first try 'noioapic', this only disables IO-APIC not all of APIC, and causes less side effects. As for side effects of turning off APIC, this may be relevant:
http://en.wikipedia.org/wiki/Intel_APIC_Architecture

Then, I may try updating the BIOS, seeing that this may indeed be a BIOS bug, but check the BIOS changelog first and see if it mentions something about APIC fixes. If it doesn't it may not be worth it.
 
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Old 03-08-2011, 01:58 AM   #3
kenneho
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Registered: May 2003
Location: Oslo, Norway
Distribution: Ubuntu, Red Hat Enterprise Linux
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Quote:
Originally Posted by H_TeXMeX_H View Post
I've gotten this message before, and sometimes it correlates with problems, and other times it doesn't. Does it cause problems ? If not, ignore it.

If it causes problems, first try 'noioapic', this only disables IO-APIC not all of APIC, and causes less side effects. As for side effects of turning off APIC, this may be relevant:
http://en.wikipedia.org/wiki/Intel_APIC_Architecture

Then, I may try updating the BIOS, seeing that this may indeed be a BIOS bug, but check the BIOS changelog first and see if it mentions something about APIC fixes. If it doesn't it may not be worth it.
Thanks for the input. I have not experienced any problems with the server in question, so I'm probably gonna leave it for now. If I run into problems I'll try the approach you described. And thanks for the link to that wiki-article by the way.

- kenneho
 
  


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