- Refer to 386 CPUs as 80386 instead of i386 since i386 is commonly used
as the architecture name rather than a specific processor.
- Clarify that 5.x also supports 80386's, just not in GENERIC.
- Note that SMP only works on Pentium-class CPUs and higher (we don't
support systems with multiple 486's and external APICs). Also, tweak
the wording to avoid saying 'supported' twice in a row.
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