Uncertain about the number of PCIe lanes you can use for your M.2 SSD
Uncertain about the number of PCIe lanes you can use for your M.2 SSD
Your setup supports an M.2 SSD upgrade. The motherboard has 24 PCIe lanes, with 4 dedicated to the chipset, leaving 20 lanes. Your GPU uses 16 of those, so you should have enough capacity for an M.2 drive without affecting GPU lanes. You're on the right track!
The remaining 4x from the CPU is allocated to the M.2 slot (usually beside the GPU), plus another 4x for the chipset, which connects to other M.2 ports on the motherboard but at a reduced speed compared to CPU lanes. As mentioned earlier, your motherboard uses PCIe 3.0 rather than 4.0 or 5.0.
When the M.2_1 Socket 3 functions in SATA or PCIE configuration, the SATA6G_5/6 connections will be turned off.
The method your motherboard uses for the lanes is crucial, so check the manual for your board to understand it. You can also install a M.2 SSD without any problems. Additionally, your chipset provides a sufficient number of PCIe lanes for other components on the board. Your board includes two M.2 slots that you can utilize here.
It's important to note that the CPU or chipset PCIe lane count isn't the main factor; instead, it's how the motherboard connects everything. The top M.2 slot is linked directly to the CPU using those additional lanes, while the bottom M.2 slot shares its bandwidth with the GPU.
On that motherboard, the initial M.2 receives four lanes from the CPU. Typically, the second M.2 gets lanes from the chipset, but the B450 chipset only provides PCI-E 2.0 lanes. Therefore, ASUS connected the second M.2 to the 16 lanes intended for the video card. If you insert an NVMe SSD into the second M.2 slot, or place a card in the second PCI-E X16 slot, the first PCI-E X16 slot is downgraded to PCI-E X8. Since no PCI-E lanes are utilized, the video card can access all 16 lanes.