dual-core vs. HyperThreading

[Michael ODonnell]

> I can definitely confirm that my core 2 quad system has no HT
> available to turn on in the bios (but does show ht in the cpuflags,
> which aligns with other comments in the thread).

I've heard it suggested several times now that features
like HyperThreading can be enabled or disabled "in the BIOS"
and I don't understand how that can be possible.  AFAIK a CPU
either does or doesn't have a given feature and there's nothing
(short of modifying the CPU's microcode) that any BIOS can do
to "disable" it, at least not in any way that would prevent a
capable OS from doing as it pleased once it was booted.  So,
what's the story?