MSI made this change in the B450 to improve performance and stability.
MSI made this change in the B450 to improve performance and stability.
I own the MSI B450 Pro gaming carbon AC and plan to add NVMe drives later. However, I discovered that using the second NVMe causes all PCIe connections to stop except for one. I compared it with similar boards from Asus and Gigabyte, but none had the same issue. Why does MSI restrict this model this way? If I had noticed, I would have picked a different manufacturer.
Many makers offer boards with restrictions on PCIe lanes based on what you fit into the M.2 slots. This information is usually shown on their official site, so it’s wise to investigate before assuming a manufacturer is at fault. For details on a specific board, open the Detail tab on its spec page: https://www.msi.com/Motherboard/B450-GAM...cification
You're questioning the accuracy of the information shared. It seems there might be a misunderstanding about the differences between various B450 models and their limitations. Let me clarify if needed.
It's not only MSI that achieves this on certain boards — many manufacturers offer motherboards with restrictions on PCIe lanes. Keep in mind that not every board will have this feature. Typically, premium boards can fit all M.2 NVMe drives while still maintaining sufficient PCIe lanes for SATA ports. Just do your research to identify models that support it.
I discovered comparable pricing with slightly lower-cost boards, similar to Asus Strix B450 and Aorus B450 Elite.
kirashi has a point, but I think the issue comes from the chipset constraints. The first NVMe drive is managed by the CPU—through a PCIe lane that’s divided by a switch. On this switch, you find the main NVMe port (m2_1) with one SATA port and two SATA slots (SATA5 and SATA6). The second NVMe is controlled by the chipset, which splits the secondary NVMe port (m2_2) and four PCIe lanes. I’m not sure how these switches function exactly, but it seems like yes or no—can’t do both at once.
In simpler terms, MSI's approach is not as effective compared to other firms.
I'd expect different configurations on other brands, but a chipset remains a chipset. Each model has its own set of features, though with certain restrictions! For the ASUS B450 Plus M.2 slot, they note the same details: only one NVMe socket from the CPU, similar to your setup. When connected, two SATA ports share the same lanes, and the absence of a second NVMe socket means other PCIe slots aren't affected by this limitation. Are you interpreting this correctly?
The Aorus Elite turns off two additional SATA ports if the second M.2 slot is full. The Asus B450-F reduces the PCIe speed of its top slot from x16 to x8. Despite supporting PCIe 3.0 x4 SSDs in the second slot, the other two drop to PCIe 2.0 x4 and 3.0 x2. Essentially, when both Carbon, B450-F and Elite have two M.2 drives, Carbon provides one PCIe x16 port plus four SATA, B450-F offers more PCIe but only x8 for the graphics card, and Elite gives more PCIe but just x8 for the graphics card. This isn't about one vendor being superior, but about how each source allocates the required connections. If you need more I/O, opt for a higher model. That's AMD's approach, managed differently by various suppliers. The Carbon also delivers the strongest power delivery.