For most of its use Inventor only uses 1 core. The main things that take advantage of multiple cores/cpus are rendering, fea and with 2012 (and newer) each idw view is rendered/calculated with a separate core.
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This isn't just an Inventor limitation, unless someone's come up with something new in the past few years that I didn't get the memo on. The problem is with any 3D CAD application, each feature in a model tree has to be fully computed before the next one can. Only one processor can work on a feature at a time, hence only one processor gets used.
I don't think FEA uses multiple cores. At least it doesn't when I use it (I REALLY wish it did...). I've only ever seen it run 1. Maybe it does in 2013, but not in 2012.
I can confirm that R2013 FEA (Stress Analysis) can utilize as many cores as your machine has for meshing and solving. It is managed by the Windows O/S multi-core technology.
Hope this helps!
Best regards, -Hugh
Simulation QA Engineer
DLS (Simulation and Material Sciences)
I agree the limitation that each feature in a model tree has to be fully computed before the next one can.
But there are many other time consuming tasks that could be distributed to multiple cores. As an example I do a lot of configurations in Inventor where one skeleton part is derived into many parts.
When I make changes in the skeleton part, perhaps 100 parts should be updated in the assembly. Each part could easily be calculated in its own process.
DSS have figured out how to use more than 1 core at part level iin Catia - so it is possible, the question is now how long will it take autodesk programmers to figure out how to do it.