Interestin g (and quite old) article about optimising for multi-core here:
http://techreport.com/articles.x/11237
I'm curious about this because it seems like a key to the games longevity, if it doesn't scale well past 4 cores, then long term increases in performance are going to be hard to come by - clockspeed improvement has ground to a halt, it seems that per-core optimisation of CPUs must be coming more difficult - so future improvements in CPUs will mostly be in number of cores.