i dont understand this whole 128-bit stuff, wanna explain? i thought for the high res 1650 screen the 512vram was supposed to help?
The bus won't simply not push enough pixels thru to run at decent frame rates at things that require 512MB vram.
Let say a game that uses 256 MB VRAM will run at 30 FPS, it will still run at 30 FPS if you have 512MB, because it only uses 256MB. Lets say you increase resolution and textures the 256MB vram will require swapping, because you need more vram to not swap from ram, the FPS will drastically fall.
The 512MB card will not have to swap, but then again, the card is not fast enough to keep decent frame rates anyway.
Here is an example stolen from barefeats.com:
Dark bars are 1920x1200 res, the other is 2560x1600
Both cards have same performance at 1920x1200, when you turn up to 2560x1600 the 256MB falls drastically, the 512MB falls a lot too, so really both are unplayable.
The macbook pro is not fast enough to have any good use of 512MB vram, it will help, but you rather turn down resolution and textures within 256MB range to get decent frame rates anyway.
If you play at 1680x1050 res, you'll won't get anything extra out of 512MB vs 256MB.