I'm guessing there will only be 9 limited edition versions of Unity for each console this time around unlike Watch Dog 10 versions each.

It's hard to find a good example since most games aren't cpu bottlenecked but this is a pretty good one:

As you can see with the slowest performing cpu's you can go all the way from 1280x1024 to 1920x1200 with essentially the same framerate. Then at 2560x1600 the gpu becomes the limiting factor and the fps drops to 70 fps across all platforms. So cpu speed limits the maximum fps, but the resolution impacts the gpu.

Resolution is jsut the amount of pixels that is rendered and that's gpu only.

I want a technical explanation and not evidence or examples from a game which details we don't know as we don't have any profiling data which part is involved in which way.

If people say this every time on forums there has to be a short and easy way to explain this by using, for example, the rendering pipeline or something similar.

I mean, thanks that you put so much effort in the reply but this is not an explanation.

Rendering pixels is a task that is handled by the gpu, and resolution is just the total amount of pixels. So if a gpu is faster(ps4's case) it can render more pixels in the same time frame(30 frames every second).

And the reason why the framerate goes down if the cpu is the limiting factor is that the gpu has to wait for the cpu to finish tasks. But as said before, that doesn't limit the amount pixels the gpu can render. In fact if the cpu really is the only limiting factor, the X1 should be able to do 1080p to because it has to wait for the cpu anyway, so it has more time to render pixels. Unless the PS4 version contains more graphical detail, both gpu's only able to handle 900p while PS4's is faster means the PS4's gpu is not fully utilized.

So Ubisoft's statement that it's the cpu that causes 900p can't be true, it can at most explains the locked 30 fps.

Thanks again but still I am doubtful that the GPU alone is to make resolution. Perhaps I need actual code which I don't expect here anyone to provide and this is totally fine but I am too curious to just believe it the way it is explained by you while not saying you are wrong.

But if the CPU really is the limiting factor and what you say is true both games should be able to achieve a higher resolution, not just the PS4 version.

Exactly and that's why Ubisoft story is probably a lie. They just opted for parity between the two versions, and they can choose to do that but it's a big middle finger to PS4 owners.

I'm not talking about a console patch.  PS4 hasn't needed fixes like making Kinect optional to give more GPU power to games; it already gave the power.

From EuroGamer:

UPDATE 7/10/14 11.40am: Ubisoft has told Eurogamer that Assassin's Creed Unity's final technical specifications for PlayStation 4 and Xbox One are actually still to be locked down.

With around six weeks to go until the game's launch, the developer revealed in a new expanded statement that there was still room for things to change.

"Final specs for Assassin's Creed Unity aren't cemented yet," a Ubisoft spokesperson explained, "but we can say we showed Assassin's Creed Unity at 900p during our hands-on preview event last week. We're confident that gamers will be thrilled with the gorgeous graphics and how Paris is brought to life in Assassin's Creed Unity.

"The development team has been hard at work delivering the best Assassin's Creed possible on next generation consoles. Regardless of which platform you're playing on, Assassin's Creed Unity will answer what an Assassin's Creed game built from the ground up for the next generation of gaming looks like and will be the best looking Assassin's Creed game ever developed."

http://www.eurogamer.net/articles/2014-10-07-ubisoft-defends-assassins-creed-unity-graphics-lock-for-parity-on-ps4-xbox-one

In the beginning, some games were gimped compared to PS3/X360 version. Now, you're right, the game doesn't come at all. But the gimping situation in the beginning is similar.

Bwahahahaha - you do believe that, do you? You don't understand a thing about programming.