Last updated January, 2018
USB risers are simple devices that allow you to move your mining GPU away from your board – rather than plugging the GPUs directly into the motherboard, the PCIe riser is plugged into the motherboard, and then a USB cable is used to connect the riser from the motherboard to the GPU.
Another advantage of the PCIe risers is that they can be plugged into a PCIe 1x slot, while the other end of the riser can be connected to your mining GPU just like a PCIe 16x slot.
As some of the best mining motherboards get more and more PCIe 1x slots, it’s becoming necessary to use longer and longer USB cables connecting the GPU risers to your motherboard. So how far can you move your mining GPUs away from your motherboard? It’s limited by the length of your USB cables, as well as your power supply cables.
PCIe Riser Cable Lengths – can you use any length?
All of the best PCIe risers come with USB 3.0 cables, and the standard length seems to be 2 to 3 feet. That’s the length I have on my mining rig, and it’s sufficient to get the GPUs up and away from the motherboard and allows them to be spaced out nicely to cool down. If you wanted to, though, you could get a much longer USB cable.
There are rumors that PCIe to USB 3.0 specifications only allow 24 inch cable length, which some attribute to the fact that most PCIe risers come with 24 inch cables. However, unlike previous USB standards, official USB 3.0 specifications don’t include any cable length limitations – it simply requires cabling that meets electrical specification. Thus, if a USB cable has AWG 26 copper wires, the maximum practical length for the riser cables would be 4.3 feet (1.3 meters).
Also keep in mind that interference can occur easier in longer cables. I have a USB 3.0 cable for my printer that is 20 feet long, and I don’t have any issues. If I coiled it up around my subwoofer though I could see it having issues.
For mining rigs, if you want to go for a long PCIe / USB riser cable, do it. Run them in straight lines, don’t coil them around each other, and you should be fine. Don’t get the flat cables, get a high quality USB cable from a reputable source. Or, buy one of the cheapest/crappiest cables you can find and test it out on your GPU mining rig, and let us know your results!