Crucial Discovers Flaw in AMD X670E Motherboards: Gen 5 NVMe Slots Drop to Gen 1 Speeds, Cause Boot Issues
Memory and SSD maker Crucial noticed an uptick in support requests by users claiming that their Gen 5 or Gen 4 NVMe SSDs would drop to PCIe Gen 1 speeds, besides being unable to boot into Windows after a restart. Crucial then did some digging, and localized the issue to users with motherboards based on the AMD X670E chipset, AMD's flagship Socket AM5 platform chipset. While not a function of the chipset itself, it turns out that there is a flaw in the way AMD designed the PCI-Express I/O of the X670E platform, specifically the PCIe Gen 5-capable M.2 NVMe interfaces that are attached to the CPU, causing them to drop in speeds to Gen 1. This problem isn't surfacing on the AMD B650 or the B650E, or even the X670—it is oddly specific to the X670E, despite the Gen 5 M.2 NVMe slots not being wired to the chipset.
While AMD made no public statement on the technical aspect of the flaw, if we were to guess, this could be a faulty implementation of PCIe ASPM (active state power management) at the firmware level, which reduces the speed of the PCIe link layer to reduce power. The default setting for PCIe ASPM in most motherboard UEFI setup programs tends to be "disabled," although there could be a bug in the firmware of X670E motherboards, causing it to engage, and in a buggy manner. Most UEFI BIOS setup programs tend to have two separate sets of PCIe ASPM settings—one for the CPU-attached PCIe root (which includes the x16 PEG and CPU-attached NVMe slots), and the other for downstream PCIe connectivity from the chipset.
While AMD made no public statement on the technical aspect of the flaw, if we were to guess, this could be a faulty implementation of PCIe ASPM (active state power management) at the firmware level, which reduces the speed of the PCIe link layer to reduce power. The default setting for PCIe ASPM in most motherboard UEFI setup programs tends to be "disabled," although there could be a bug in the firmware of X670E motherboards, causing it to engage, and in a buggy manner. Most UEFI BIOS setup programs tend to have two separate sets of PCIe ASPM settings—one for the CPU-attached PCIe root (which includes the x16 PEG and CPU-attached NVMe slots), and the other for downstream PCIe connectivity from the chipset.