Messages in this thread | | | Date | Tue, 10 Jul 2001 08:26:09 -0700 | From | "Randy.Dunlap" <> | Subject | Re: How many pentium-3 processors does SMP support? |
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Chris Wedgwood wrote: > > On Tue, Jul 10, 2001 at 04:19:43PM +0200, Christoph Hellwig wrote: > > The number of CPUs is currently globally limited to 32 by NR_CPUS in > include/linux/threads.h. > > Really? > > <pause> > > Ah, so it is... yes, making this architecture dependant might be a > good idea. Large PPC and MIPS boxen need to adjust this already. Also, > someone did a starfire port, I think that had 64 processors, not sure. > > You can. But you cannot buy 32-processor PII (-Xeon) systems that are > supported by Linux. > > What is the limit here? The 8/16 way SE chipsets? > > > In anyone from Compaq is reading this, you should send me a 32-way > > Xeon ASAP just to prove they really work :) > > It doesn't. > > Oh, then they definately need to send me one. > > Are these not MP1.4 based? Something different? > > --cw
For IA32/i386/x86:
The Linus-kernel only supports a maximum of 15 Pentium IIIs due to APIC addressing (4 bits, with 0xf meaning "broadcast").
Pentium 4 uses 0xff for broadcast, so lots more of them can be supported (when you can find a P-4 MP server).
I have heard of some IBM/Sequent patches that modify the logical vs. physical APIC addressing scheme to make 16-way systems work.
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