The devkit have 8GB memory to use... now they have 16GB... they are running in devkits and the final build will use less than 4GB for sure... maybe less than 3GB.

Now they can run the game with 9-10GB use in the new devkit.

But the console has 8gb, so how can they use 10? I dont understand. :(

Wait isn't the extra RAM in dev kits usually taken up by the debugging and performance analysis tools? And surely it would be considered bad practice to use more RAM than final hardware for the game, especially when they go out of their way to say "no cheats".

They will not 10GB... they use that in dev times and for the final build a lot of memory optmizations are done so the game uses a lot less memory than in dev times.

They worked with a target of 3GB (1GB is for the OS) and the demo running in a dev machine used 4.6GB of RAM but the final build will use less than 3GB for sure... now they will work with 7GB (or 6GB) so they will have the demo running in 9-10GB and after the memory optimizations the final build will run in less than 7(or 6) GB.

That my guess.

Memory optimizations, compression and others stuffs are not cheats...

They said in the slides they not did optimizations in memory yet... so they are using more than the final game will use.

Well that is my guess looking the slides.

I know a code running in debug mode uses more RAM than the normal... they are running in debug with other apps to trace everything that happened with the game running.

You can tell they are getting GPU limited with the demo, due to the fact it's only 30fps and the AA method used. (However, it's still early days, but that's their framerate target anyway.)
Then, to make 30fps feel smoother, they added blurring techniques and this Demo has a bit of blurring on the objects and characters, not very pronounced in the video, but it is there.

If you look back at the Xbox 360 and PS3 launches, most games were in a similar situation, most running at 1080P initially, but when you start adding more effects and geometry, sacrifices had to be made and one of those eventually became the resolution after a few years into the consoles life, overall graphics did look better though, so it was a sacrifice that was well worth it from an overall perspective.

Man, I wish it would come to PC though, so we can dial-up the graphics, framerate and resolution more, with that said, I'm actually looking forward to getting my hands on a PS4, new uncharted trilogy perhaps?

Well they made no CPU optimization for now.

About the memory I found something interesting...

Form the 4.6GB at least 600MB is not to use from memory... it is supposed the be streaming directly from HDD (like dialogs) but Guerrilha is using a pool in memory... than can change in final build.

And about the CPU the guys in B3D are saying that the devkit was running at 1.6Ghz and Killzone using 6 threads... that information was analysing the profile output.

I meant running over 1.5GB over their presumed memory target would have been a cheat. 

All streaming engines I know of use a pool in memory for streamed content, it's basically a cache for the in use files. You can manually tweak the pool sizes in ini files for Unreal engine games on PC.

I wonder if the PS4 has 2 cores locked for OS and background tasks. They used one SPE in the PS3 but the PS4 is doing a lot more demanding stuff in the background.