Did you know what lies behind the USB 3.0 or Thunderbolt controller? It's of course the bus that connects it to the rest of the system, PCI-Express. It is the 500 MB/s per lane interconnect that is indirectly responsible for the awesome bandwidth that today's plug and play interfaces such as eSATA 6 Gb/s, USB 3.0, and Thunderbolt 10 Gb/s enjoy. What if you could eliminate the protocol overhead that comes with any of those protocols, and make PCI-Express directly an interconnect? So thought the PCI Special Interest Group (SIG), the body that decides the fate of PCI. The SIG is planning to create a cabled version of PCI-Express Gen 3, that has no secondary protocol overhead, not even of the kind Infiniband has.

A single PCI-Express 3.0 lane can provide 8 Gbps (1 GB/s) of bandwidth in each direction, the new cabled interconnect can supply bandwidth of four Gen 3 lanes, totaling 32 Gbps, over three times that of the current version of Thunderbolt. Apart from that bandwidth, cabled PCI-E will be designed to supply 20W of power to its devices, plenty of power for even a small 3-bay HDD rack. The connector itself will be designed to be very compact and flat, so it can be fitted into notebooks and tablets. PCI SIG plans to have the first specifications of cabled PCI-Express ready before June 2013. By 2013, Intel will be about 2 years away from releasing its proposed 50 Gbps version of Thunderbolt, but even then, Thunderbolt is an additional protocol that sits over the system bus (again, PCI-Express), unless Intel designs Thunderbolt controllers to somehow talk to CPU over QPI.