Several M.2 boards designed to operate independently without overlapping data transfer rates.
Several M.2 boards designed to operate independently without overlapping data transfer rates.
You're trying to upgrade your system by swapping out the Asus X99a motherboard for an i7 5280K CPU and adding a new ASUS Z490E ROG board. You're facing some issues with your NVMe drives not performing equally, which suggests the board and CPU might be sharing bandwidth. You're considering a build with an AMD 5800X CPU and PCIe 4.0 slot, possibly using a larger drive. You're also planning to upgrade to a higher-end CPU later and have some storage in mind. Your main concern is whether a PCIe 4.0 board can handle two NVMe drives at full speed each. You're cautious about overclocking and want to avoid damaging your system. Keep it simple—just want reliable performance without risking hardware issues.
I don't know why you get half speed for the second slot. Both have pci-e 3.0. The ports are not sharing the lanes. The 1st one gets its lanes from the CPU and the other got its lanes from the chipset. So it suppose to run at full speed in all slots. If you're using 970 evo you will not be using pcie 4.0 speed, as the drive is a pcie 3.0. Full atx AMD boards usually have 2-3 m.2 slots being 1 connected directly to the cpu. I suggest getting a X570 board if you want full pcie 4.0 support for all the slots.
Its description in the manual but the ROG z490 board I owned shared the lanes on the M.2, so when testing them, one M.2 (Samsung EVO 970 500GB) gave full speed while the other (Samsung EVO Plus 1TB) slowed to half. Swapping them didn’t change the outcome. I could achieve full speeds on slot 0 for M.2, but slot 1 only gave half speed. I’m looking for a board that supports running two M.2 drives at full speeds together.