A modern ultra-high-end gaming PC manages 16Gb/sec between the CPU and GPU.

The Xbox360 manages 21.6Gb/sec and the PS3 manages 25.6Gb/sec (those are not accurate, but they’re close). It’s why a game console can do so much with just a 8-ROP-based GPU at 550Mhz.

Both Microsoft and Sony know what gaming consoles need: memory bandwidth and massive bandwidth between the CPU and GPU [Memory]. All other consideration were rescinded; although it’s a known quantity that the top game developers have been pushing both Microsoft and Sony about the very limited memory amount that they had included for the 1st and 2nd Dev Kits.

3rd Generation Dev Kits have been reported having 12Gb of DDR3-type memory – but that is main memory and not GPU-GDDR-type memory.

The thought here is that some form of fast DDR3 256bit memory will be shared between then CPU and GPU, and not GDDR5 for example. 4-8Gb of 256bit GDDR5 is just too complicated to use in a low power, compact, game console. If you had 14nm fabrication tech going into it, it wouldn’t be such a problem; 28nm seems to be the indication.

DDR3 256bit is capable of 192Gb/sec without pushing boundaries too far in terms of voltage and heat.

The GPU memory in the Playstation Orbis/Omni has been subtley hinted at by Sony to be 192Gb/sec of ‘some kind of memory’. Sony have clearly stated several times that “bandwidth is the key”.

Knowing what the GPU is going to be in these consoles doesn’t really matter. All that matters is the game developers have told Microsoft and Sony that they need an absolute minimum of 2 Teraflops of compute power generated by the CPU and GPU.
And that is what is going to happen.
There are strong indications from those in the tech forums that they’re trying to get this figure up to 2.5 Teraflops, but that 0.5 is more power than the Xbox360 and PS3 combined.

The gap between 2 Teraflops and 2.5 Teraflops and the limitations of low-power per watt, are huge and difficult.
2.25 Teraflops seems to be the halfway point they’re reaching for.