Date: Fri, 29 Nov 1996 12:17:03 +0800 From: Peter Wemm <peter@spinner.dialix.com> To: vanmaren@fast.cs.utah.edu (Kevin Van Maren) Cc: drussell@internode.net, smp@freebsd.org Subject: Re: P5 vs. P6 performance Message-ID: <199611290417.MAA10448@spinner.DIALix.COM> In-Reply-To: Your message of "Thu, 28 Nov 1996 08:15:13 MST." <199611281515.IAA13282@fast.cs.utah.edu>
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Kevin Van Maren wrote:
>
> While we are on the subject of CPUs... Can you do SMP with the Cyrix 6
x86
> chips?
>
> Later...... <Doug>
>
> Short answer: No. Cyrix and AMD proposed a competing standard for
> SMP, called Open PIC. However, I talked to AMD folks at COMDEX, and
> they said that not only had they given up on Open PIC, but that they
> only care about the low end. He also mentioned that he thought that
> Cyrix was going to give up on Open PIC (this is good for us, as we
> won't have two competing specs to support), but it was unclear from
> the AMD guy if, and when, Cyrix would finally add an APIC compatable
> with Intel's (most likely have to license it).
Well, as I understand it, the APIC "invention" is patented to the hilt
which pretty much precludes cloning of it without licenses.
I've read the OpenPIC stuff, at least superficially, and it looks like it
wouldn't be all that much hard work to use it, but it's definately
something that we don't need to deal with right now. Considering that the
APIC design at present is partly in the CPU and partly on the motherboard,
and I'm not aware of *any* motherboards with an OpenPIC interrupt system
in them, I'm skeptical of whether it's even worth worrying about right now.
However, that doesn't mean the situation won't change in the future. I
certainly won't be doing anything that's going to prevent any chance of
support for it being written.
Having said that, we're discovering the magnitude of the difficulties that
we're facing in the kernel proper, even after we've got the low-level
stuff sorted out. It's starting to look pretty much like the lower layers
(APIC, OpenPIC etc) are going to be a small fraction of the work that's
needed in the big picture.
Cheers,
-Peter
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