PCIe slots on any motherboard come in two sizes referred as PCIe 1x and PCIe 16x, you have to buy a riser card with appropriate size to your motherboard. ... The 1x size allows only one connection per PCIe lane at a time. This might affect performance while gaming, but it does not harm mining performance at all.

Do PCIe risers affect Hashrate?

If connected through the full PCIe 16x slot, this 295 KH/s limit is non-existent, and the more you overclock past that same amount of MHz as before, the higher the hash rate.

Are GPU risers good for mining?

When it comes to cryptocurrency mining, risers with standard PCIe 2.0 x16 slots are the most popular ones. Since PCI-E risers are used to connect multiple GPUs to your mining rig and thus increase overall mining performance, they also require a reliable power delivery in order to power up all those GPUs.