Messages in this thread | | | Date | Thu, 8 Jan 2009 16:10:46 +0100 | From | Ingo Molnar <> | Subject | Re: Is 386 processor still supported? |
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* Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> > > Hmm. Where in Kconfig is SMP for M386 not allowed? > > > > Dunno, kconfig is too much of a jungle for a simple person like me ;-) > > > > But afaik i386 (and possibly i486) don't support nearly enough for a > > modern SMP system. > > > > Alan used to have i486-smp I think, one of the very few ever made. > > The first systems that supported the Intel MP standard are 486 based > with external APIC. The prior systems used various proprietary MP > interfaces from the simple stuff in the Compaq (which Linux doesn't > support as Compaq refused to allow Thomas Radke to contribute it) to the > fairly extreme end of things with the Sequent boxes. > > In addition our FPU emulation and some of our handling for x86 > processors where we have to do the WP bit in software is also not SMP > safe. > > So our minimal spec for SMP is probably 486DX + external Intel APIC. > > In practice I doubt there is a single Intel APIC type 486 SMP box on the > planet running Linux (or quite possibly running at all)
yeah, that's very likely true. I think we could eliminate some of the SMP complications by requiring cmpxchg presence for CONFIG_SMP, agreed?
Ingo
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