We have some quad cores - with ATI 1900 ( Tiger ) and some eight cores with 8800 ( leopard ) Strangly, but the Tiger can run 4 layers of 1080p AIC and the Eight cores, 3 layers... sometimes 4.
Just as an example,... we had a event wich the movies are BLACK and WHITE, and we achived 5 layers of 1080p... so all depends on the content.