Ok... will try to see what I can make with these new info.
I was reading a bit about IO-APIC and Local APIC. Frankly, it does goes above my head (not fully understanding, not so much interested).
At this site: http://osdev.berlios.de/pic.html I am reading something that looks like could be related to my computer:
"Oh did I say one more thing? There's more. Some motherboards have a thingy that you must write to redirect the interrupts from the 8259's to the IOAPIC. This is done by writing 0x70 to port 0x22 and 0x01 to port 0x23. Also, you may want to disable the 8259's completely. I do this by writing 0xFF to ports 0x21 and 0xA1. So I disable the 8259's first, then program the IOAPIC, then write the ICMR (0x22,0x23) ports to accept IOAPIC interrupts."
Maybe this motherboard need the: outb 0x70, 0x22 outb 0x01, 0x23 ?
Don't know if Linux is aware of that and try it.