" The PCI Express 3.0 standard has been with us rather longer than anyone intended it to be. The standard was initially finished in 2010, and motherboards supporting it were in-market by 2011. PCI Express 4.0 should have been available by 2013 if the organization had kept to its previous pace, but delays and difficulties associated with the design have left PCIe 4.0 support languishing. Now PCI-SIG has announced that PCIe 4.0 specification is finished — and it plans to have PCIe 5.0 ready to go by 2019.
That’s an accelerated launch window and, given the relatively short window between completing the standard and shipping hardware (typically about 12 months), it’s not clear if PCIe 4.0 will find a huge home in the market. PCIe 5.0, according to the standards body, is coming along quite quickly. "
" With 64GB/s of unidirectional transfer bandwidth, PCIe 5.0 would deliver more bandwidth than dual-channel DDR3 interfaces. Heck, it would deliver more bandwidth than DDR4-3200, though at far higher latencies (nobody is going to be building PCIe-connected RAM any time soon). Even though GPUs are primarily the only devices that use x16 slots, quadruple the bandwidth per lane means that x1 and x4 products would still benefit from these gains. High-performance network and SSD solutions could both use the bandwidth, and PCIe 5.0 would put the industry ahead of even Nvidia’s high-speed NVLink technology.
With PCIe 4.0 only being finished now, we wouldn’t expect to see motherboard manufacturers integrating it until 2018, and that could take longer if AMD and Intel don’t bake support into their own upcoming products. Given that most CPUs have on-die PCI Express controllers these days, getting that kind of capability baked into hardware refresh cycles rests more on the CPU vendor than motherboard company, though the mobo manufacturers do need to do the work of validating their board designs. If PCI-SIG hits its target goal of a 2019 standard finalization date, PCIe 5.0 could be in-market by 2020 or 2021."