lol, ok didn't want to make this more complicated but now we agree that the memory bandwidth wouldn't change whether you had one truck or two as it would still take the same amount of time to fill it and return I'll now explain why I said two trucks. I said two trucks because i didn't want to drift away from the fact that in reality you do have two physical amounts of memory but the memory, or sand in this case, needs to be in seperate trucks so the the person shovelling has easy access to the sand without the other person getting in his way. Now as the memory is mirrored both trucks have sand rather than one having sand and the other gravel. This is because they must throw sand into the sea for half the day and gravel for the other half, the times that sand or gravel gets thrown in can not change but the amount of sand or gravel gettting thrown can change. It's the same with memory, even though you have 1 gb on each card the data stored on that 1gb must be the same so that the required data for that period is avaialbale to both cards and they can both use that same data and effectively process it twice and so render twice as many frames. but the essential data itself still remians identacle for both cards and can only be collected when both cards require it so is not collected twice as fast (memory bandwidth).