According to Micheal Brown on comp.lang.asm.x86, "For
multiprocessor 486 boards (and some early Pentium SMP
boards, supposedly), the "local" APIC is a chip
(82489DX) that is seperate from the CPU itself. Most
486's don't support CPUID, and even if they did I don't
think they would report the presence of a local APIC.
Obviously you don't need to worry about the Pentium/K5
as these should report the APIC status
correctly in the CPUID instructions. I'm unsure about
cyrix chips though.
"For the 486's, you can probably detect the presence
through probing the APIC address space and checking
things like the APIC ID and the like. Otherwise, if you
can find some docs about the 82489DX you might find
some extra information in there."
There is apparently no free documentation for the
82489DX chipset (Google didn't find any, and none seems
to be available on intel.com or x86.org) so for the
time being, I won't be able to develop any code for
this chipset unless someone is willing to donate the
book about this chipset or develop the necessary code.
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