CFD: XMLification of NOTES

[Bruce Evans]

On Wed, 31 Mar 2004, John Baldwin wrote:

> On Tuesday 30 March 2004 06:54 pm, Dag-Erling Sm=F8rgrav wrote:
> > CPU_I386 should not conflict with SMP, but a kernel build with both
> > will be very slow.
>
> No, it does conflict.  There's no cmpxchg on i386 and no one has had the
> desire or time to emulate one for 386 machines.  Doing so would be a wast=
e in
> my opinion as well.

des only claimed that it "should not".

Emulating cmpxchg might make a kernel built with both slow, but the
current CPU_I386 only adds a tiny amount of slowness.  It just doesn't
work on multi-CPU systems if multiple CPUs are actually used.

Does it actually conflict in practice (except for the forced #error)
if the hardware is UP?  jhb's APIC changes made configuring with SMP
not require APIC, so SMP kernels work on UP systems.  Configuring with
I386_CPU shouldn't affect this, but it does because of the forced #error
at compile time.

Bruce