That site most likely queries direct x for the vram size. I would recommend checking if gpuz shows the same. That or run a game that is graphically demanding while using afterburner to monitor vram usage to see if 512mb is still available to the apps.
Edit: just so you know where I'm coming from. When doing hardware surveys in the past steam and blizzard have both reported incorrect vram size even though there was nothing wrong with the card or programs using the card.
Last edited by dicertification; 2011-11-14 at 12:08 PM.