I have an x86-64 computer running Linux that I would like to supplement with other non-x86-64 Linux machines.
Is it possible to somehow benefit from the computational power of another machine without it being the same architecture?
As a second question, what kind of performance increases are available and does it require specialized software to work? Or can Linux just abstract the cluster / additional machines as additional CPUs?
As Henri said, you need the software to take care of the different representations. That rules out MPI, but for example NWS (which you can use with Python, R, Matlab, …) should work.