Yes, async compute is what Mark Cerny thought would keep the PS4 relevant as these under powered consoles begins to age.
http://www.gamasutra.com/view/feature/191007/inside_the_playstation_4_with_mark_.php?print=1
http://www.anandtech.com/show/9124/amd-dives-deep-on-asynchronous-shading
Alright then, so I'm not behind on the times. A bus that can simultaneously read and write does not exist or does not exist within the next generation consoles.
So the BW increase is a result of adding read/write speeds to ESRAM? I didn't know bi-directional busses were a real thing.
And by bi-directional, I mean the ability to read/write at the same time.