The PCI SIG — a special interest group of engineers and vendors focused on advancing PCI Express file transfer protocol — plans to develop a PCI Express-based interconnection standard for external computing devices in a move that may eventually compete against Thunderbolt, which was co-developed by Apple and Intel.
The new standard will be based on PCIe 3.0, which supports transfers up to 8Gb/s. The proposed external PCI Express specification will support four streams at a transfer speed of up to 32Gb/s at distances no longer than 3m.
Initially, the interconnection will use copper wires, but eventually, as the speeds get higher and when the technology adopts the PCI Express 4.0 protocol, the connectivity may be changed to fiber optics. The proposal will likely result in a 16Gb/s version based on PCIe Gen4 in about four years and an optical version for longer range and/or higher data rates at some point in the future.
PCIe 3.0 will not support devices with a power consumption higher than 20W, which means that it will be impossible to implement external graphics cards into the power envelope of a single port. With this limitation, the connector will only support mass storage devices such as solid-state drives, flash cards, external disks and cameras. It would, however, be physically possible while utilizing several ports with separate power supply circuitry.
The group is expected to deliver a standard that can be built into products by June 2013. PCI SIG is seeking to position its external PCIe 3.0 for thinner consumer devices with higher speed cable interconnection. A major part of the work ahead will be defining technical requirements and designing a new connector.
Representatives of the PCI SIG declined to comment in any way on Apple’s Thunderbolt technology. “This will help proliferate PCI Express into new business opportunities. Right now we see a need from our members,” Al Yanes, president of the PCI SIG, told EE Times.
“The big issue here is proprietary versus industry standard. It is not clear third parties will have access to Thunderbolt on the same basis they get access to PCI Express,” Nathan Brookwood, the head of Insight64 analyst firm of Saratoga, CA, told EE Times.
The motivation for the PCIe cable “wasn’t spawned due to Thunderbolt, it was more about the shift to thin notebooks and tablets that means you just can’t mechanically package things the same way we used to,” said one source close to the effort who asked not to be named.
Thunderbolt uses a router chip on either end of the connection to support multiple protocols and daisy chaining of devices. Apple “is fine with the extra cost of the router chips, but we don’t need the multiprotocol support, and a couple extra chips don’t make business sense for us,” the source told EE Times.
Apple and Intel introduced Thunderbolt in February on a line of MacBook Pro computers. Since then the technology has spread to other Apple models. Thunderbolt supports two 10Gb/s bidirectional channels on a common transport layer that can carry 4x PCIe Gen 2 or DisplayPort traffic.
