Check if it supports PCIe 2.0 or 3.0 via the second M.2 slot.
Check if it supports PCIe 2.0 or 3.0 via the second M.2 slot.
I have an Asus Prime X470 Pro board and recently added a second NVMe M.2 drive, which in turn removed an expansion card. I reviewed the manual to find out which slots shared clocks and relocated the card—everything seems fine now. While going through the manual, I came across a confusing note I don’t grasp. I’m puzzled about this: X470 uses PCIe 2.0, yet it claims to support 3.0 lanes? And why only two lanes instead of three? My initial guess was that a switch might be combining two 2.0 lanes into three 2.0 lanes, but that seems overly complicated without any benefit. I checked the MSI X470 Gaming Plus manual, which lists it as 2.0 4x, so why would this model differ? At first, I thought the Asus guide might have an error, but HWiNFO shows the new SSD controller connected via the chipset at 3.0 2x, which makes sense. So both seem to offer the same bandwidth, just I want to understand how it actually functions.
I understand the distinctions between generations 2, 3 and 4. X470 is from generation 2 (you know). I think it links to the CPU via four lanes of generation 3—though maybe not fully there, that could be generation 2 too. All what comes after the chipset follows generation 2.
Reviewed Asus' website; the specified slot operates as intended. Storage options include 3rd/2nd/1st Gen AMD Ryzen™ and 2nd/1st Gen AMD Ryzen™ with Radeon™ Vega Graphics. It supports M.2 Socket 3, M key, and accommodates various storage devices (SATA & PCIE 3.0 x4). The system features AMD Athlon™ with Radeon™ Vega Graphics, 7th Gen A-Series, and an Athlon™ X4 processor. There are two M.2 Socket 3 ports, each supporting up to 6 SATA 6Gb/s connections and compatible with RAID 0, 1, or 10. The M.2_2 slot shares PCIe clock with PCIe x1_1; if x1_1 or x1_3 is in use, it restricts it to SATA mode. This configuration reflects AMD's mainstream design limits—only 24 PCIe lanes available, GPU supports 16 cores, and the first M.2 slot uses 4 lanes, leaving limited capacity for other components. The trade-off is evident in the *2 notation.
Typically, with X370 and X470, from the eight SATA connections the motherboard can offer, two can be used for PCIe 3.0.
Yes, a motherboard manufacturer has options between SATA Express and PCI-E 3.0 with two lanes.
Thank you for your feedback. I appreciate the clarification. It was important to understand how it worked with the X470 chip-set, and your question helped me grasp the details. mariushm's response matched exactly what I needed.