Rambus (yes them) claims to have got the fastest gddr6 memory working in the market, thanks to a new phy chip. Their GDDR6 runs at 18 gigabits per second, with which a maximum bandwidth of 72 gigabyte... Rambus Achieves GDDR6 Performance at 18 Gbps
Rambus Reports Second Quarter 2019 Financial Results-Business Wire:"we remain well positioned as the first-mover for next-generation DDR5 server DIMM chips, shipping samples at the top-end speeds for both the RCD and DB chips"