If it cannot be used effectively, then why would the manufacturer market it as a 1GB card? What makes it not able to use 1GB of ram effectively?
its marketing trick. nvidia and ATI build their cards differently and architecture changes from series to series. most people are easily confused by all of this so they tend to buy the card with the most RAM thinking its faster. PCs are sold the same way, toss more ram in the PC to make it seem faster.
why can't the 4670 effectively use 1GB of ram? it has to do with its gpu chip, stream processors and the rest of the card's architecture. its just to slow to effectively use it. its like having a long bed pickup truck and a 1.7L v-4 engine.