The PCI Special Interest Group is working on the PCI Express 4.0 standard, which would double the maximum transfer rates to 16 gigatransfers per second. PCIe 4.0 would be the last standard based on copper, with a move to optical board superseding it. Detailed requirements are still up in the air, but the speed targets are thought to need new chips to properly feed boards longer than 10-12 inches.
One PCI SIG member believes PCIe 4.0 boards with one connector will need re-driver chips to cover distances longer than ten to twelve inches. Current maximum distances cover 20 inches and two connectors will need re-driver chips. The new spec should also lower power consumption, as it needs less hardware and physical space.
The president of PCI SIG, Al Yanes, believes that PCIe 4.0 will eventually be used by anyone who now uses a four- or eight-lane original PCI Express design. The first adopters of the technology are expected to be high-end graphics and networking makers. Yanes also believes flash drives will use it.
What will be retained from current 8GTps version 3.0 technology is its encoding, which should also preserve the same overhead and throughput for apps. Simulations to determine maximum throughput took up to nine months, with 16GTps judged to be the optimal for the copper-based boards. Speeds up to 24GTps would make the technology too expensive.
Goals include low cost and backward compatibility, Yanes said. The team is also looking into ways to improve active and idle power use.
The standard should be completed by 2014 and the first systems using it are expected to ship in 2016. Based on the group's regular four-year gaps between releases, the optical boards are expected out in or near 2019.