Why GFX card with more RAM?

[SEE]

Great post FS_Phat, thanks for keeping and posting those comments and reminding us all of the technical challenges this sim imposed!

One more question, what is the relationship between the GFX card and the CPU with regards 'bottlenecking'? Is this simply a GFX card whose performance outclasses the CPU and thus has to wait for X amount of CPU cycles and seen as stutters, drop in FPS etc and why the use four cores should have a major advantage of say two?