ATI plans to power their RV770 XT with 1GB memory, and when it comes to the XT card we are talking about 1GB of quite fast GDDR5 memory. The RV770 PRO is also possible and will launch in its 1GB iteration, making it possibly more attractive to end-users. ATI counts on the good old logic that implies that bigger is better and more memory doesn't really makes the card much faster, but at least it doesn't hurt either. The standard RV770 XT and PRO comes with 512MB but some partners will launch 1GB versions. The chip itself can address even more than 1GB but we guess apart from a good marketing buzz you can create with a 2GB card, you don't really see the performance benefits. - FudZilla

ATI RV770 XT High Speed 1GB Video Card Upcoming

The RV770 version A11 from ATI, which is usually a pre-production version, needed 1.26V to work, and it looks like the ATI boys did improve the A12 chip. The A12 revision, which is the one that ATI usually ships to market, only needs 1.13V, which means it's significantly cooler and can be clocked higher. Both voltages are referring to the samples clocked to 625MHz, but we have a strong feeling that the final units will work at higher than 625MHz. The clock details are something that the company finalizes shortly before the launch. The RV770 XT and PRO are the mainstream chips that will also create the high-end R700 card.