As I say -- all later manuals have an error here (not the first and
presumably not the last one), where they state the invalid register error
has been only implemented since the P6. This is not true -- go find the
Pentium manual or experiment with actual hardware to see otherwise. No
new bits have been added since the introduction of the ESR, so there is no
issue with bits to mask out on older silicon.
Obviously the checksum and accept error bits are valid for APICs using
the dedicated inter-APIC bus only as for the FSB they are irrelevant.
They have to be hardwired to zero for backward compatibility though.
Maciej
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