Our sources, some time ago, told us that Zen will use a DDR4 PHY capable to support up to DDR4 3200 MHz (or 3600 MHz thanks to AMP profiles), and the new DDR4 PHY of Rambus supports these frequencies. Also, recently

Rambus has achieved the first production-ready 3200 Mbps DDR4 PHY available on GLOBALFOUNDRIES power-performance optimized 14nm LPP process, the same process AMD will use to produce Zen (According to most recent rumors): “Together with GLOBALFOUNDRIES, we have been able to develop the industry’s first DDR4 PHY on a 14nm LPP process running at 3200 Mbps and capable of achieving the performance requirements of next-generation systems […] GLOBALFOUNDRIES’ FX-14™ platform, based on our advanced 14nm LPP technology, is designed to support the memory intensive computing tasks in today’s most demanding enterprise applications”. Last, but not the least, in January AMD has extended patent license agreement with Rambus.