PCIe DOUBLES ONCE AGAIN

Version 4 spec released, and 5 is announced

THE FINAL SPECIFICATIONS for version 4.0 of PCI Express have been released, and once more we’re treated to a doubling of bandwidth. PCIe 4.0 runs at a base speed of 16GT/s. This translates to a little under 2GB/s per lane, so your x16 graphics card will get a healthy 31.51GB/s of bandwidth to play around with. As ever, it’s fully backward compatible. This has been a long time in the making; it was first announced in 2011.

Faster is better, of course. NVMe cards and RAID systems will be happy, but most current hardware is comfortable with PCIe 3.0—it takes some serious gear to hit the buffers. Initially of more use is that you can halve the number of lanes for the same performance, saving those precious lanes for where you really need them. This is particularly important for processor PCIe controllers—these get full fast access to the CPU, and are in short supply. For example, many dual graphics card rigs have to share a x16 link, which is beginning to stretch the PCIe 3.0 specs.

Along with the healthy speed bump, we get a host of tweaks, lower latency, better scalability, RAS, and so forth. We also have OCuLink-2, a cable standard similar to Thunderbolt, which can take PCIe lanes where needed. Power is up, too. It’s still 75W from the slot, but it allows for more than 225W extra direct from the PSU, although details are sketchy as yet. Before you get too excited, all this is some way off. We need PCIe 4.0 controllers in consumer processors first, and that is probably still years away. AMD has slated 2020, Intel hasn’t committed yet, but is certainly keen to get Optane on to a faster bus.

It doesn’t stop there, though—version 5.0 has been outlined as well, and this doubles things yet again. The PCI Special Interest Group is talking about 2019 for this. However, given how long version 4.0 took to cook, we can probably take that with a pinch of salt.