The AMD X399 Chipset and Quad Channel memory
The X399 Chipset
While some of the chipset functionality is harbored inside the processor, a new generation and architecture processor will always require a new motherboard chipset. Let me first reiterate and make clear that ALL Ryzen processors are unlocked, that entails all Ryzen 3, 5, 7 and thus now the new Threadripper processors. Threadripper processors however will require a new socket due to the many pins needed. The platform will be using Socket design SP3r2, a 4094-pin socket that was originally developed for the AMD Naples (EPYC) series server processors, but again, AMD did a 180 and is introducing it also as high-end desktop platform series processors and chipsets.
The massive processing power that Threadripper offers is balanced by more memory bandwidth via quad DDR4 channels, and it’s backed by up to a whopping uncompromising 64 PCIe 3.0 lanes for things like multiple graphics cards, many ultra-fast NVMe SSDs and fast USB and Ethernet. Threadripper ready motherboards will come with 8x DDR4 DIMM modules that can hold a total of 128 GB of DDR4 memory and you will often see 4x PCIe x16 slots and support for up to three NVMe M.2 drives on these motherboards as, well, the motherboard manufacturers have enough PCIe 3.0 lanes to work with. PCI-Express Gen 3.0 is fully supported on all 64 PCIe Lanes, that means you also get 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.
As such the X399 chipset will support multi-GPU rendering (Crossfire and SLI) with up-to four mechanical x16 PCI Express slots (Gen 3.0) and connected from there onwards endless possibilities in your configuration, say, 16x/16x/8x/8x Gen 3.0.
The Ryzen Threadripper processor has an I/O of 64 PCIe 3.0 lanes. The interlink inbetween the Threadripper processor and X399 chipset is a 4x PCIE Gen 3 link - and then your X399 chipset will also offer additional 20 (!) PCIe Gen 2 lanes and 12 (!) SATA3 ports. Again, four lanes function as an interconnect to the chipset. In the above screenshot you can check how that works out compared to Ryzen / X370.
Quad channel DDR4 Memory
AMD brought DDR4 support to Ryzen 3 5 and 7, but that remained dual-channel. With Threadripper that quad-channel support is being introduced. The motherboards will be paired with eight DIMM slots, configurable as single, dual and quad channel setup. AMD will support the standard Jedec SPD timings and frequencies at 2133/2400 and 2667 MHz, but you can expect to see motherboards with support for 3200 MHz (and higher up-to 3600 MHz) as well, much like Ryzen with AGESA 1006 and newer offers. Two channels per two 4 DIMMS per 2 dies and will offer UMA (distributed) versus NUMA (local) modes (for low gaming latency). The new memory subsystem will run 3200 MHz in quad-channel with no problems (with compatible memory).
AMD's Memory configuration options - Uma (Distributed) or Numa (Local)?
With everything that is going on with Threadripper you already know that the physical size and layout of the processor is big. That also means some DIMM DDR4 channels are closer, while others are farther away from the memory controllers. You could describe that as near memory and perhaps far memory based on the distance of the two processor chips and its cores inside the package. Near memory has a latency in the 77ns range while far memory can pass 120ns. AMD’s solution is to use Ryzen select (in BIOS or Ryzen Master) two memory modes that.
UMA is the Distributed Mode memory control - it is the platform default and allows software to use all the DRAM evenly. Local Mode NUMA uses local memory near the die or chip to gain lower 66.2ns latency. Obviously the number of modules of memory installed is trivial here, but we assume most end-users will use 4 DIMMs in quad-channel.
This option will become available in Ryzen Master, but you can use the BIOS option to switch between the two memory modes. Generally older/less threaded games might run slightly faster in the Local mode while latest games/heavily threaded games (e.g. Ashes) will run better with the default Distributed mode. Very simply put, Distributed mode offers better bandwidth, Local mode offers lower latency. Our advice, play around with it a bit and run both modes to get the complete picture and select your preference. We can see Gamers end up at Local mode and, say, video editors at the default Distributed mode.