Ubisoft has revealed that they have done a better work optimizing their new Assassin's Creed title for the PC, which happens to be the platform receiving the worst of Ubisoft with every generation of new game titles. Well, things will be different his time round. At least, that's what Ubisoft promises.
"There was a major optimization pass that was done on the engine, not just for the PC, but for every platform. The scheduler used for the rendering was rewritten from the ground up. In AC4, the engine will use all the cores it needs until it sees that using more cores brings no more gain. So, yes we should expect better performance on PC than AC3, especially on DX11 hardware."
With AC4, the game engine has added support for the powerful DirectX 11 API, which has been available for over 4 years now (high time Ubisoft made a move to it and updated their Anvil Engine accordingly). It's possible that the updated Anvil Engine supports DirectX 11.2 and AMD's Mantle, but we'll have to wait a little bit longer to find that out.