Hello everyone! I'm just new here... I just want to ask what is the difference between a 256-bit and a 512bit video card. Does the amount of bit greatly affect the performance of the video card? What are the pros and cons? I'm really sorry!! it is kinda noobie question... hehe!
For a single card solution, the higher the bus the better the performance, generally.
For a multi-card setup, the larger the bus, the lower the scaling efficiency, as the bus size will effect how saturated the PCI-lanes will be. Two 128 bit cards (like the 5770 for example) will be better bang for the buck with near 100% increase in performance with adding a second card. But, if you start with a higher performing card (like a 5850) and add a second one, there is far less than %100 increase (closer to 70% in this example) in performance, due mainly to saturation of the PCI lanes, from its larger bus.