Computex 2022 | Enthusiast AMD Ryzen 7000 goes full PCIe Gen 5 with two daisy-chained X670 ASMedia PROM21 chipsets, A620 to launch later alongside Rembrandt desktop APUs

Socket AM4 had a long run with AMD Ryzen CPUs starting with Ryzen 1000 Summit Ridge to the present Ryzen 5000 Vermeer generation. Today's launch of Ryzen 7000 Raphael at Computex 2022 marks the transition to a new socket and platform.

AMD chipsets for Ryzen codenamed Promontory have been traditionally made by ASMedia with the exception of the X570 chipset, codennamed Bixby, which was made by AMD in-house with ASMedia IP. AMD had to make Bixby in-house as its suppliers were not yet ready for the PCIe Gen 4 era. Therefore, AMD repurposed the I/O die on the Matisse and Vermeer CPUs into a dedicated chipset capable of supporting Gen 4 speeds.

This resulted in a product that wasn't quite power or thermal efficient, and it even required active fan cooling. Now that PCIe Gen 4 has become fairly commonplace, with AM5, AMD is once again turning to ASMedia for the sole production of Zen 4 Raphael's X670, B650, and A620 chipsets.

Apparently, AMD wanted to outsource AM5 chipset development to both ASMedia and MediaTek but is likely to stick with ASMedia for the most part. It is not fully clear whether we will get to see any MediaTek chipsets at all, at least in the initial phase.

Zen 4 Ryzen 7000 I/O

Ryzen 7000 CPUs offer plenty of I/O on their own including (via Angstronomics):

• 1x PCIe x16 slot for graphics (or bifurcated to two x8 slots)
• 1x PCIe x4 slot for M.2 NVMe SSD
• 1x PCIe x4 link for discrete USB4 controller (Maple Ridge JHL8540 or ASMedia ASM4242) or M.2 NVMe SSD
• 1x PCIe 4.0 x4 for chipset downlink
• 3x combo USB-C ports supporting USB3.2 Gen 2 10Gbps and DisplayPort 2.0 UHBR10 Alt Mode (each combo port can be split into discrete DP and USB 2.0 Type-A)
• 1x additional dedicated display output (DP 2.0 UHBR10 or HDMI 2.1 Fixed Rate Link or eDP)
• 1x USB 3.2 Gen 2 10Gbps port with BIOS flash capability
• 1x USB 2.0 port with SecureBIO support for Windows Hello capability
• SPI/eSPI, GPIO, HD Audio

Three Promontory 21 chipsets for Zen 4 Ryzen 7000 AM5

The AM5 platform supports a total of 24 PCIe Gen 5 lanes, up to 14 USB 3.2 Gen2 ports, HDMI 2.1-out, DisplayPort 2.0-out, and Wi-Fi 6E with Bluetooth 5.2. The exact configuration will vary depending on the motherboard model.

Once again, we get to see three chipsets for the Zen 4 Ryzen 7000 AM5 platform:

• A620: Low-end PROM21
• B650: Mid-range PROM21
• X670: High-end dual-PROM21

A620 is expected to launch later, possibly when Rembrandt APUs make it to desktop. Compared to the B650, the A620 will have one PCIe Gen 4 x4 downlink disabled.

AMD B650 chipset

The AMD B650 is aimed at mainstream price points and will support PCIe Gen 5 storage (from the CPU). It will be a single-chip solution. Specifications include:

• 19 x 19 mm FCBGA package
• Maximum Power ~7W
• 1x PCIe 4.0 x4 Uplink to host
• 2x PCIe 4.0 x4 downlink controllers (Total 8 Lanes)
• 4x PCIe 3.0 x1 / SATAIII 6 Gbps flexible ports (4L PCIe or 2L PCIe + 2x SATA or 4x SATA)
• 6x USB 3.2 Gen 2 10 Gbps ports (Two of the ports can be fused to form one USB 3.2 Gen 2x2 20Gbps port, with four remaining 10Gbps USB ports)
• Up to 6 additional USB 2.0 ports

AMD X670/X670E chipset

The interesting part, however, is the X670 chipset. AMD offers the flagship chipset in two flavors: the regular X670 and the X670E. Both are identical in terms of hardware, but the X670E is pegged a complete PCIe Gen 5 solution with the requirement being that the first PCIe slot and first M.2 slot should support PCIe Gen 5 speeds.

Another unique aspect of the X670 chipset is that it is arranged in a daisy chain: one X670 connects to the CPU while another links to the primary X670.

Daisy-chaining is beneficial for AMD/ASMedia to maximize yields with a single tapeout while helping increase I/O for end users. This also helps with reduced heat and negates the need for an active fan and additional signal retimers for components far from the CPU. 

However, daisy chaining also brings complications in the form of potential hiccups in I/O virtualization and another point of failure. We will have to wait and see how AMD's dual-chipset solution pans out in the long run.

USB connectivity issues on B550 and X570 chipsets are not new. Users are likely to connect their mission-critical USB devices directly to the Ryzen 7000 CPU before making sure the new chipset architecture poses no problems.

Specifications of a dual-X670 PROM21 chipset include:

• 2x 19 x 19 mm FCBGA packages
• Maximum Power ~7W x 2
• 1x PCIe 4.0 x4 Uplink to host
• 3x PCIe 4.0 x4 downlink controllers (Total 12 Lanes)
• 8x PCIe 3.0 x1 / SATAIII 6 Gbps flexible ports (4L PCIe + 4x SATA or 2L PCIe + 6x SATA)
• 12x USB 3.2 Gen 2 10 Gbps ports (Four of the ports can be fused to form Two USB 3.2 Gen 2x2 20Gbps ports, with eight remaining 10Gbps USB ports)
• Up to 12 additional USB 2.0 ports

Connecting Wi-Fi 6E and Ethernet to PCIe Gen 3 will free all 12 PCIe Gen 4 lanes.

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