and what's the difference between 5770 and 6770 (just name difference or what?)
More about512mb ddr5 ddr3
The HD 5670 is not powerful enough to take advantage of 1GB of RAM regardless if it is DDR3 or DDR5. Based on benchmarks, at most a HD 5670 1GB card will give you 1 extra frame per second.
The basic differences between the HD 5770 and HD 6770 are: 1. All HD 6xxx cards are only PCI-e 2.1 card. No PCI-e 2.0 cards are produced. 2. The HD6xxx cards have HDMI 1.4a connections as opposed to 1.3c. Generally speaking it can handle 3D movies and 3D games.