Graphics card question

[nst7]

I'm a mac guy with a question for windows guys.

If I remember correctly, a while back I remember seeing a few threads about how graphics cards should not go above 512 of memory (I forget what the issue was) for a computer that uses protools. What I'm wanting to know is if that was specific for windows, or what the specific issue was.

The reason I'm asking is Apple just released new Imacs, and they now have discrete graphics cards (up until now they were always integrated). And if you order the top-line I7 quad core, the graphics card has 1GB of memory (no customization to make it less).

I didn't know if that would be an issue, because I don't remember what the issue was on windows, or if it would even apply to a mac.