The PCI Express standard has been one of the most successful in the computer market, meeting user demands with each new generation without sacrificing backward compatibility. Right now, the best we have at our disposal is version 3.0, but starting next year we'll witness the debut of PCI Express 4.0. By reaching a new limit of 16 gigatransfers per second, the PCI Express 4.0 bus anticipates a combined bandwidth of 64 GB/s, and believe it or not, they're already thinking about its replacement…
A Look Back at PCI Express
Unless it's a compact computer with more specific functions in mind, any modern motherboard should offer some PCI Express slot to the user. Whether the plan is to connect a graphics card (its most common role) or an alternative component like a solid-state drive, the fact is that it's a too powerful bus, and it must be taken advantage of. Its adventure began in 2004, when the AGP port still ruled the graphics world, and the differences were so wide from the start that PCI Express 1.0 at half throttle could match the bandwidth of AGP 8x. Revisions to its specifications didn't take long to arrive, and the available bandwidth kept growing without abandoning backward compatibility, something we never tire of demanding. However, this progress stopped in 2010. PCI Express 3.0 managed to adapt without major hiccups to modern hardware (with graphics cards using controllers as large as an operating system), but there are no plans for it to end there, quite the opposite.
PCI Express 4.0 and Beyond
The specifications of the new standard PCI Express 4.0 are in "version 0.9", meaning it only depends on a final certification. Unlike what happened between PCIe 2.0 and 3.0, PCI Express 4.0 effectively doubles the speed, reaching 16 gigatransfers per second. In slightly friendlier terms for us, the total bandwidth of PCI Express 4.0 x16 rises to 64 GB/s. PCI-SIG confirmed that the new version will have optimizations in flexibility and scale parameters, designed for low-power devices and applications requiring even tighter latencies. If all goes well, the first products with PCI Express 4.0 support should hit the shelves before the end of the year, but my bet is in the first quarter of 2018.
Now, the most interesting thing is that we won't have to wait that long for the replacement version, PCI Express 5.0. Unfortunately, we can't say much on the technical side, but the idea of doubling the bandwidth remains firm. PCI Express 5.0 will have a cap of 128 gigabytes per second. Can you imagine a graphics card or a solid-state drive using that full bus? The best is yet to come.
