First off the AMD HD 7770 is a low end card and the HD 7790 is an overclocked version of the HD 7770 however they both come stock with GDDR5 ram as standard..
-The Xbone has the equivalent of an HD 7770, is a slower gpu in comparison with GDDR5 memory but Microsoft decided to make a slow gpu in comparison slower with DDR3.
DDR3 its old and slow for todays GPU standards, its not even close to the speed of GDDR3 either..
DDR3 is great and fast for system memory, operation system, multitasking and whatnot, but not up to standard for GPU intensive graphics at higher resolutions at a higher settings,, it would be much harder for the DDR3 memory to render stuff fast while trying to keep those frames per second above 30 at 1080p without pop-ins and less likely to achieve 60 without cutting corner (lower settings) and sub 720p to make that game look good and playable.
Doesn't matter how people would try to spin it, the nature of this, DDR3 clock per clock, bandwidth speed per speed, DDR3 is years behind GDDR5 design architecture.. as far back as gpus with DDR3 from 2006 - 2008.
For example: 2gb GDDR5 clocked @ 800mhz vs 2gb DDR3 clocked @ 1200mhz, guess who's faster? clock speed don't matter. the architecture of these memory type is like night and day.
The PS4 has the equivalent of an HD 7870 with GDDR5 memory, its a mid range card and a great performer .. would not compare both as this wouldn't be fair ..
The card alone on the PS4.. graphics card vs graphics card without the memory. The 7770, again wouldn't be fair to compare it with the 7870. it would a joke if someone tries to compare these two GPUs as they stand now ..HD 7770 ddr3 vs 7870 GDDR5.
No matter how Microsoft or anyone would try to spin it, game developers and computer programmers know that faster is better .. I guess Microsoft never had the thought of including at the least GDDR3 for their GPU, its still slower than GDDR5 but I assure you it can run circles around DDR3 memory.
And to think of Microsoft will carry the XBONE for the next 7 to 10 years .
My Trigger Happy Sixaxis controller
