Originally posted by: Wouter Liefting
It's been a long time since the number of cores matched the number of sockets. Even the humble Power4 already had two cores per socket, and so did Power5 and Power6.
Power7 has eight cores per socket, although you can also get four- and six core per socket variants - you'd have to look at the order form for your hardware to see what you've got exactly, if the HMC doesn't show a total processing capacity that's a multiple of eight. (And with TurboCore mode you can turn half of the cores off, so the others can use more cache and a higher clockspeed.)
Power8 will have twelve cores per socket
That's just what's in the box. Whether your application is actually *using* these cores and/or sockets is a totally different matter. It depends greatly on the partition profile (entitlement, capped/uncapped, shared/dedicated, #VP, MSPP settings, ...) but within the constraints of the partition profile the hypervisor also has some leeway on where to place the workload. So one day you might be using, say, two cores that are on the same socket, and the next day you might be using two cores that are on different sockets.
The only real way to see what's going on and to have some measure of influence over this, is to use tools like ASO and DSO.
It is well worth learning about this stuff in-depth, or getting a consultant that knows about this stuff in-depth. I know companies that have literally saved 100s of 1000s of euros by taking a careful look at the exact licencing conditions, and optimizing placement of licensed applications so that the required performance was reached with minimal resources.
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