23 April 2014

Next-gen Thunderbolt details: 40Gbps, PCIe 3.0, HDMI 2.0, and 100W power delivery for single-cable PCs

Light Peak (Thunderbolt)

For the last few years, Intel and Apple have worked to create an ecosystem around Intel’s Thunderbolt interface, formerly known as Light Peak. The first generation Thunderbolt interface offered four independent lanes at 10Gbps down a single cable, while Thunderbolt 2 allowed those lanes to be combined into two 20Gbps channels. It looks like Thunderbolt 3 (codenamed Alpine Ridge) further doubles up on performance by increasing bandwidth to 40Gbps (around 5.1GB/sec). That’s enough bandwidth for multiple 4K video streams off a single controller or ultra-fast high end PCI-Express SSDs or at least, it will be if Intel fixes the backhaul problem.

Intel Alpine Peak

Check the listed features and you’ll note that the new standard is PCIe 3.0 compatible. That probably means that it supports the PCI Express 3.0 standard for remote graphics cards, but frankly we’ll be more excited if it also supports PCIe 3.0 for the actual motherboard link. Both Thunderbolt and Thunderbolt 2 relied on a single PCIe 2.0 x4 connection, with a peak maximum bandwidth of 1.6GB/s. While that’s sufficient for most modern hard drives, hanging a secondary GPU off a PCIe 2.0 connection and then attempting to drive a high end monitor off it isn’t going to fly at 4K.

PCI Express 3.0 support for graphics card enclosures is a nice marketing bullet point, but PCIe 3.0 support for an x4 linkage between the TB controller and the motherboard would actually matter as far as high end graphics performance.

The other two major features of the new Alpine Ridge controller are its support for HDMI 2.0 (allowing for 4K resolutions at 60Hz) and the implementation of a 100W power delivery capability (just like the USB Power Delivery spec). This will allow companies like Apple to build single cable MacBook products there won’t be any need for a separate power connector for charging the device. Other PC manufacturers could also follow suit, though high end laptops with more than 100W of power consumption will continue to rely on separate bricks. Intel is also promising sharply reduced power consumption and two different controller SKUs, presumably to give manufacturers a lower cost option.

Thunderbolt’s long term strategy

Alpine Ridge is expected to debut alongside Intel’s Skylake chipsets, which won’t arrive in market until 2015. By that time, the USB consortium expects to have USB 3.1 shipping in hardware. USB 3.1 is the next-gen USB standard that doubles the maximum transfer rate to 10Gbps and will provide up to 100W of power as well. While that bandwidth is far below Thunderbolt’s maximum configuration, 800-900MB/s of usable bandwidth would still be sufficient for virtually any external enclosure. Multi-drive SSD arrays might test that bandwidth, but precious little else does.

A 40Gbps signal rate could potentially open Thunderbolt up for other uses, however, including HPC connectivity. While fabrics like Infiniband will continue to dominate large scale deployments, Intel is still working on the optical technology it originally intended to debut with Thunderbolt/Light Peak. That could buffer the design if the Mac Pro’s all Thunderbolt architecture doesn’t take off.

MXC Connector

In early March, Intel announced its new MXC connectors that support up to 1.6TB/s of bandwidth per cable (25Gbps per fiber, 64 fibers per cable). The new standard hasn’t been explicitly discussed as part of the Thunderbolt specification, but it’s not hard to see where Intel is going. As Thunderbolt matures, Intel is simultaneously emphasizing both increased bandwidth and lower power consumption both of which are vital to exascale computing.

Intel hasn’t announced availability for the MXC connectors or cables, but Corning has already released a 10 meter Thunderbolt 2 cable far longer than 1-2 meter copper cables that the interface typically uses.

courtesy extremetech


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