This is strange! The apic is in the cpu since the pentium (I think so) and I also changed because of that my board, because the bios also deactivated the apic
You needn?t to deactivate acpi (and you can?t) it is only used for detecting cpus and io-apics if it is not available I use the mps.
I have not to understand the reasons for this!
The problem is that I have 1 kernel and this kernel is able to work on uni and smp systems and if I use the apic on both systems it is easier for me to code.
Edit::
Tomorrow I will have time, so maybe I will give it a try and write some code to support pcs w/o apic enabled. But the last time I tried it, it didn?t work