The first Zen-based chips are expected in early 2017 and the first Socket AM4 motherboards are hitting the channel. TechPowerUp spreads photos of two Gigabyte motherboards, one seems to use the entry-level A320 chipset while the other one sports the mid-range B350 chipset.
The first of the two GIGABYTE AM4 boards is built in the narrow micro-ATX form-factor; featuring a single PCI-Express 3.0 x16 slot, two DDR4 DIMM slots, four SATA 6 Gb/s ports, and basic connectivity that includes 6-channel HD audio, one gigabit Ethernet connection, and 4-6 USB 3.0 ports. The second board is better endowed, and is likely a variation of the socket AM4 board that was earlier pictured this September. It features two PCI-Express 3.0 x16 ports (the second one could be electrical x4); and comes with two additional SATA 6 Gb/s and USB 3.0 ports compared to the other board.
The new high-end chipset for AM4 is the X370, we'll probably see a lot of motherboards based on that chip as we get closer to CES 2017.