Impact of PCI bus speed on opencl performance

PCIe 4 is expected in 2016. Can anyone comment on the impact this will have
on gpgpu performance? For gaming, I have read that pci 3 has about same perf
as pci 2.

Short answer: It will improve things.

Long answer: Of course for big data bandwidth-limited problems where compute has been overlapped with transfer but the transfer is very large it will be a huge improvement. For other work, if transfer has been overlapped with compute but not taking longer than compute, it will make no difference at all. I expect most real-world problems fall somewhere in between these extremes.

Overall, everyone needs to upload and download data so any bandwidth improvement is welcome.

Thanks, Dithermaster. Makes sense.