just put 2
cause that's all you have.
no need to have room for more that you have. (kind of a no brainer)
I'm not really sure about the rest of it and i am as far from an expert on this stuff as one can get.
but this is kind of the types of things involved.
obviously with capacity for more cpus the code structures for acpi, interupt handeling, soft riqs, scheduling and cpu affinity all just have to be that much larger. I think it's not really that the interupt routing table is going to end up bigger but that possibly the structures pinting to the interupt handeling
tables have to be bigger. It may also be that some of the underlying (low level) ram paging structures need to be a bit larger in order to accomodate cpu specific data if there are lots of cpus.