That is because you would still be running the same program. If you run a static program it will hit a point were more power does not make it look or run noticably better. This is not the same as giving devs more RAM. Giving devs more RAM means they can add more to there program.
More RAM for devs means:
-Higher res texture
-More detailed enviornments
-Longer draw distances
There is plenty more that they can do with extra RAM in the development of a game.
Games are not running on 1.5GB of VRAM because they can go any higher, it is due to PC games being restricted by the mass market spec. Right now games are built for PS3/360 and low end laptops. They are then scaled up from there for things like the GTX 680. With the PS4 and hopefully the XB3 having 8GB of RAM this will give devs a new mass market spec.
GPUs with 3 and 4GB of RAM are fairly new to the market, and they will start to see that be used very soon. It will not be long before 6, 8, 10, and 12GB cards are on the market. By the end of this gen you will see games running on much more VRAM. 1080P PC games will probably be using 8 - 10GB of RAM, and we will see 4K resolutions pushing 16, and I feel this is a minimum.
Just fixing your post a little:
More RAM for devs means:
-Added effects - NO! You would need a faster GPU for that.
-More animations - NO! You would need a faster CPU for that.
-Higher res texture - YES. You can include higher res textures with more RAM.
-More NPC - NO! You would actually need a faster CPU for processing more AI. If they use repeated textures, then extra RAM will not help out at all.
-More detailed enviornments - YES. But only because of what you already mentioned before with the higher res textures.
-Longer draw distances - YES. It helps.
That all depends on how much they were even using the CPU/GPU with 4GB of RAM. Was it a scenario like last gen were they had already ate up all the RAM and the CPU/GPU were craving more? I think it had to be, and thats why devs started begging for the 8GB. Now they may have more than they need, and there optimization can focus on enhancing the game rather than how to squeeze more into a tight RAM pool.
So to clarify;
Everything you corrected in my post was true, in a system that was pushed to the max, but this is not a system in that situation. Even if they had the same CPU/GPU/RAM they could improve all of those areas greatly just due to optimization. This added RAM allows them to do all of those thing better, because now they can optimize the game engine, and add more/ improve more without the need to waste CPU power cramming the extra features into a undersized RAM pool.
It is halarious to see people saying that this extra RAM is going to have limited effect. This system is going to be on the market having new games made for the next 6 to 8 years. In that time they are going to learn a lot about this system, and they will learn how to make that extra memory do wonders.
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