Hello and welcome to the forums
The answer is yes, and if you read the FAQ on top of the graphic section,it will answer your questions http://www.tomshardware.com/forum/245454-33-crossfire-f...
"Do SLI or CrossFire double the memory ?
This is one the questions that many people make mistake understanding it .
The answer is NO , SLI or CrossFire doesnt double the memory , You have a 512MB card , adding another card wont make your memory 1GB, it still will be 512MB,so both cards will use 512MB of RAMs but the memory won't double.
Another example :
A game needs 512MB card to run at maximum settings , and you have a 256MB card , and you think if you add another 256MB card , your memory will be 512MB and that's not true."
You are welcome
The reason is that when you put 2 cards in SLI/CF,each card run simultaneously,so for example if you have 2 512MB cards,each will operate with 512MB of memory,but it doesn't make the total graphic memory 1GB. And no,no drivers can fix it, because its anything that can be fixed or changed.