PCH - The Platform Controller Hub Chipsets
The X399 Chipset is designed for Threadripper processors, holding the Socket design SP3r2, a 4094-pin socket that was originally developed for the AMD Naples (EPYC) series server processors. The X399 chipset powered motherboards come with quad channels memory up to a total of 128 GB DDR4 memory and whopping 64 PCIe 3.0 lanes for things like multiple graphics cards, many ultra-fast NVMe SSDs and fast USB and Ethernet. The new chipset also gets full support for the NVMe protocol, USB 3.1 Gen 2 (10 Gbps) and M.2 and SATA Express support. Since Ryzen architecture processors have all the IO paths and a controller built in for USB 3.1 (Gen 2) as well, there will be PCI lanes dedicated to your NVMe needs.
The Ryzen Threadripper processor has total 64 PCIe 3.0 lanes. The interlink between the Threadripper processor and X399 chipset is a 4x PCIe Gen 3 link. The X399 chipset will also offer additional 20 PCIe Gen 2 lanes and 12 SATA3 ports. Other PCI Express slots are distributed to support multi-GPU rendering (Crossfire and SLI) with up to four physical x16 PCI Express slots (Gen 3.0) and running configuration of 16x/16x/8x/8x Gen 3.0.