Well, Xgrid can be used on OS X 10.4 - 10.7, so its not exactly ancient technology; or at least its several decades newer than most other topics discussed here

Interesting read http://en.wikipedia.org/wiki/Xgrid

Edit: It looks to me that the performance of the controlling computer has to increase with relationship to the size of the cluster/complexity of computations, since

its task is to distribute the work and assemble the returned results.