I think you should look into a task- or job-basedd approach.

Game Engine Gems has 2 or 3 articles on the subject.

There have been a couple of presentations on the subject at different conference etc.

For example "Parallel Futures of a Game Engine" by Johan Andersson

Also take a look at the GDC Vault there are a number of presentations and full videos on the subject in the free section. http://www.gdcvault.com/

ps. Couldn't post any more direct links due to being a new user. ds.