The analogy to a core for DRM, 1 for apps, 1 for antivirus isn't too far off...

Having tested multicores for quite a while now, even single threaded apps can see a great improvement when run with an SMP OS. Each new process started will be placed on the least busy core, and while a core is tied up doing I/O other processes that aren't awaiting I/O can run at full speed.

Classic tightly coupled SMP tests show a significant roll off after 8 processors without SMP aware apps, but up to there you get almost a multiplier effect for each new added core so long as memory and I/O bottlenecks are avoided.

This *does* depend on your OS being good at multiprocessing.