When AMD teased its upcoming Ryzen 7000 (Raphael) processors for the AM5 socket, the chipmaker indicated that the Zen 4 chips support DDR5 and PCIe 5.0 interfaces. However, AMD did not say whether PCIe 5.0 will be supported only by the upcoming CPUs or by both processors and AMD's 600-series chipsets. So, for now, it looks like PCIe Gen5 is reserved only for CPUs.
This week it transpired that PCI-SIG had validated the interoperability of AMD's 600-series AM5 chipsets with PCIe 4.0 x4 devices at a 16 GT/s data transfer rate, which may indicate that the company's next-generation core logic does not support PCIe 5.0. Considering that ASMedia designs AMD-branded chipsets, it will not be shocking that the development is somewhat out of sync with AMD processors since the two companies use different interface IPs.
PCIe 5.0-supporting chips validated by PCI-SIG are Intel's Alder Lake and Sapphire Rapids processors, Intel's FPGA, Phison's PCIe 5.0 redriver, and Samsung SSD controller's 1743 SSD, and various IP modules by Broadcom, Cadence, and Synopsys. Unfortunately, there are not so many PCIe Gen5-supporting devices on the market right now. For AMD, a more pressing issue is to validate its upcoming desktop platforms with PCIe Gen4 devices because it is a more widespread technology and AMD needs this certificate to meet the requirements of PC OEMs.
Alternatively, the lack of PCIe Gen5 validated interoperability may mean that AMD's 600-series chipsets cannot handle PCIe 5.0 in their current form, which is why AMD/ASMedia will need to build another silicon revision free of specific bugs or limitations.
One thing to note about PCIe 5.0 is that it is incredibly complicated to support 32 GT/s data transfer speeds. It is possible to use redrivers to ensure signal integrity over long distances in servers. Still, it will be prohibitively expensive with desktops, so ensuring ideal PCIe 5.0 implementation by chipsets is crucially important. If AMD's 600-series chipsets indeed have specific issues with PCIe Gen5, it may not make sense to enable this technology at all. After all, AMD's AM5 processors will support PCIe Gen5 anyway.