Re: [PATCH 2/2][2.5]Unisys ES7000 platform subarch

From: William Lee Irwin III (
Date: Wed Jun 11 2003 - 11:52:38 EST

On Wed, Jun 11, 2003 at 11:40:05AM -0500, Protasevich, Natalie wrote:
> Clustering on ES7000 follows Intel guidelines, but not quite fall into
> certain cluster model category. According to Intel book, cluster can be flat
> (on the same bus) or hierarchical (physically separate bus segments). Flat
> cluster uses serial bus messaging (like on xAPIC systems) and can support 15
> agents. On both APIC models that ES7000 utilizes, it can support 32
> processors (with xAPICs, 64 hypothreaded P4's, if only OS could support
> that). It has special arrangement for the APIC buses and corresponding
> numbering for APICs, which reflects its topological nature, so the
> conventional APIC cluster numbering schema won't work. Due to those
> differences, our clusters are not that "flat", and we call it "physical",
> and "logical" really means "hierarchical". I think, our cluster model names
> came from some previous distributions that implemented both models, I swear
> I didn't invent it myself. They just worked for our case.

This nomenclature has also been used by other large i386 system vendors
besides Unisys, e.g. Sequent.

-- wli
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