One of the problems SSDs are facing in the computer market is that they're getting too fast, too soon. It's largely a luxury problem, a couple of years ago people still lamented about how slowly storage evolved versus the rest of the industry and now people are scratching their heads to figure out just how all this storage performance will fit into your PC.
As PC World writes today, fast new storage solutions like the Intel 750 series are pretty much pushing the limits of what's possible in consumer PCs as there's just not enough PCI Express bandwidth to go around on the Intel Z97 chipset if you also want to do multi-GPU. The expensive X99 solves this but even on that platform you may still run into bandwidth bottlenecks if you have an ultra-high-end system with three or four video cards.
The only path for us today and in the near future is occupying a PCIe slot. It’s the easiest way to get to the most performance, and more bandwidth can be added by just adding lanes. The Intel 750 drive, for example, uses four PCIe lanes in PCIe Gen 3.0 mode.
The problem there is what happens when you run more than one graphics card. with a drive as fast as the Intel SSD installed, a typical consumer gaming box will cut the bandwidth to the video card in half. Granted, most games and most video cards don’t really use all of that bandwidth. But what happens when that gamer wants to run the Intel drive with two video cards? To paraphrase Dana Carvey paraphrasing George HW Bush: “It’s not gonna happen.”
And so the wait is on for PCI Express 4.0. This specification is expected to be finalized in 2016 with adoption planned for the years thereafter.