The new interconnect method will offer nearly seven times more performance than the traditional PCIe interface: four Global Memory Interconnects (GMI) will reportedly offer a latency-free 100GB/s link between the CPU and GPU, much more than the 15GB/s at about 500ns latency provided by PCIe x16.
The first MCM with the coherent fabric will reportedly feature a Zeppelin CPU (presumably with Zen-based cores) and a Greenland GPU with High Bandwidth Memory (HBM) on the same chip package. The slide below reveals the Greenland GPU promises 4 teraflops of raw computing power and mentions there's a 500GB/s link between the GPU and the HBM.
The chip will support DDR4-3200 memory, which will talk to the CPU at the same 100GB/s. The product is expected sometime in the 2016-2017 timeframe.
Source: FUD Zilla