Luckily unless you're doing something odd with your GPU it isn't using the bandwidth and won't lose significant performance either way.
Steve from gamers nexus tests new GPUs on older PCIe gens and the difference is negligible. And since PCIe always doubled bandwidth with generations it's effectively the same as running on half bus speed.
I run an Intel A380 for Linux and a NVIDIA 3060 for a Windows VM (I'm a bit cheap). I opted for using some Intel SATA6 datacenter drives we decommissioned from work over using more PCIe for storage, but the performance is outstanding.
Modern game engines don't need all those gigabytes per second. If you're doing AI maybe it matters, but then you probably hopefully maybe won't cheap out on consumer CPUs with 20 PCIe lanes either.
Low-end GPUs often only have eight PCIe lanes to begin with, sometimes because they're using chips that were designed more for laptop use than for desktop cards. Intel Arc A380 and B580, AMD 7600XT, NVIDIA 4060Ti and 5060Ti are all eight-lane cards.
I do really think we're due for an expansion refactor. 75 Watts is an awkward amount of power and PCBs are worse than wires for data throughout and signal integrity. It feels like GPUs would be much happier if we just had a cable to plug into the motherboard that transferred data and no power and which didn't force the GPU to hang off the side of the motherboard and break during shipping
Steve from gamers nexus tests new GPUs on older PCIe gens and the difference is negligible. And since PCIe always doubled bandwidth with generations it's effectively the same as running on half bus speed.
I run an Intel A380 for Linux and a NVIDIA 3060 for a Windows VM (I'm a bit cheap). I opted for using some Intel SATA6 datacenter drives we decommissioned from work over using more PCIe for storage, but the performance is outstanding.
Modern game engines don't need all those gigabytes per second. If you're doing AI maybe it matters, but then you probably hopefully maybe won't cheap out on consumer CPUs with 20 PCIe lanes either.