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The AM4 Platform
AMD announced its AM4 interface and corresponding chipsets during the Bristol Ridge launch. Previously, core logic was a weak point, as the 9-series chipsets lacked a lot of modern features available from Intel's platforms. Moving forward, all Ryzen CPUs share the same socket. This gives you a number of options for building a Ryzen-, Bristol Ridge-, or future Zen+-based system.
Similar to Intel's platform controller hub architecture, AMD pushes integration with the move to Socket AM4 and tasks its chipset with functions typically associated with southbridges. Meanwhile, it adds more capabilities to the processor die you wouldn't expect to find there. For instance, Ryzen 7 1800X provides four USB 3.1 Gen 1 ports. It also offers 16 lanes of PCIe 3.0 we're guessing most enthusiasts will use for graphics, along with four lanes of second-gen PCIe for SATA 6Gb/s and NVMe storage. In time, we may even find board vendors building platforms based on just the CPU's I/O.
Intel's Core i7-6900K doesn't expose any USB connectivity directly. Rather, it relies on X99 and attached controllers to enable those ports. On the other hand, Broadwell-E packs up to 40 lanes of third-gen PCIe for a lot more flexibility in what you attach. Ryzen's ability to split its 16-lane PCIe 3.0 link into two x8 slots looks a lot more like Intel's mainstream chipset line-up in comparison.
AMD breaks Socket AM4 down into five different chipsets. Enthusiasts will want to pick up X370. B350 targets the mainstream crowd, whereas A320 goes the locked-down route for "essential" builds. For those of you who anticipate deploying APUs in HTPCs and LAN boxes, X300 and A/B300 should address those markets (we're still waiting on their specifications).
Given Tom's Hardware's focus on the enthusiast and mainstream markets, our motherboard reviews will emphasize X370 and B350. The two platforms are differentiated in much the same way AMD positioned the old 990FX and 970: a higher-end chipset gets you extra I/O, mostly. X370 includes four extra USB 3.1 Gen 1 ports, two additional SATA 6Gb/s ports, and two more second-gen PCIe lanes. Moreover, B350 doesn't allow you to split the 16-lane PCIe 3.0 link into two slots like X370 does.
Both Socket AM4 platforms support overclocking out of the box though, in addition to RAID 0/1/10 and two SATAe ports. AMD's documentation notes that SATAe ports can be broken up and re-purposed for additional SATA ports or second-gen PCIe lanes, potentially opening the door to larger storage arrays or additional M.2 ports.
According to AMD, the Socket AM4 interface will carry it through 2020. By then, technologies like DDR5 and fourth-gen PCIe should be prevalent, paving the way for newer platforms.
