Dual Opteron Upgrade Question

[marc.miller at amd.com]

Scott,

Make sure you are buying an Opteron 200-series processor along with a dual-processor capable motherboard.  Not all dual-processor motherboards will work; some (such as the Tyan K8W S2885) try to distribute the load on the hypertransport bus by hanging the IO chipset off of one processor and hanging other HT chipsets off of the other (the AGP bus in the example of the Tyan S2885, though theoretically this could also be the PCI-X chipset or any other Hypertransport (HT) device).  It's a fantastic strategy with two processors, but with only one, the absence of a processor would then eliminate that functionality.  There is nothing there connecting the chipset to the rest of the HT bus.  If it comes down to a choice between AGP or PCI-X and IO, I recommend keeping the IO.  ;)  Not populating one processor socket also means you will lose access to the memory slots associated with that socket.  

Having said that, if you can do without that functionality, I can't think of a reason why it wouldn't work.  We tested several of the early AMD64 motherboards with only one processor populated and everything worked fine.  


As for what Red Hat product to put on the machine, any product should do nicely.  I don't know of a Red Hat product that doesn't have a kernel that you couldn't use with multiple processors.  When you want to switch from a uniprocessor kernel to a multiprocessor one, you simply `rpm -e uppackagename` and then `rpm -i smppackagename.x86_64.rpm` the new kernel.  

I was really hoping someone from Red Hat would answer your question, since the one thing I don't know for sure is whether the installer has to set up anything outside of the kernel to enable NUMA optimization for AMD64 once you have multiple processors (the kernel is supposed to allocate memory for a process to the bank connected to the processor where that process is running).  

Despite all of the documentation available on Andi Kleen's 2.4 NUMA kernel, I just don't know if Red Hat did it the same way.

If you don't care about NUMA optimization, switching the kernels should be all you need to do.  I can't imagine there being anything that would require a complete reinstall.  

> -----Original Message-----
> From: amd64-list-bounces at redhat.com [mailto:amd64-list-bounces at redhat.com]
> On Behalf Of soul
> Sent: Wednesday, August 11, 2004 1:55 PM
> To: amd64-list at redhat.com
> Subject: Dual Opteron Upgrade Question
> 
> I am building a server and it will eventually be Dual Opteron.  To keep
> cost
> down I would like to only buy one proc at this time and upgrade to dual
> proc
> later.  Can I perform an install such as that when I take it down and
> upgrade it with the second proc that it will take advantage of the new
> second proc without having to reinstall.  I really don't want to invest
> the
> extra money at this time.
> 
> If this is possible, which product should I install on the server?
> 
> Thanks,
> Scott
> 
> 
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