Dear Sirs, I put together a 3GHz P4 XEON APIC v16 on a Shuttle FB61 main board with Redhat Linux 9 (kernel 2.4.20-8 smp). dmesg says "unexpected IO APIC" with a suggestion to send the message to linux-smp@vger.kernel.org . I have attached the output of dmesg to this e-mail. I do not notice anything wrong with this computer running Redhat in spite of the error message. Yours sincerely Stephen Blake