, then USB
and now PCI Express. It's clearly the era of version 3.0, and given that the PCI Express specification has been humming along at 2.0 speeds
for over two years now, we'd say an update was definitely due. Thankfully, the PCI-SIG has announced the availability of the PCIe Base 3.0 specification to its members today, and the highlights are certainly notable. There's a new 128b/130b encoding scheme and a data rate of 8 gigatransfers per second (GT/s), doubling the interconnect bandwidth over the PCIe 2.0 specification. And since we're sure you're fretting it, we'll go ahead and affirm that it maintains backward compatibility with previous PCIe architectures. We're also told that based on this data rate expansion, "it is possible for products designed to the PCIe 3.0 architecture to achieve bandwidth near 1 gigabyte per second (GB/s) in one direction on a single-lane (x1) configuration and scale to an aggregate approaching 32 GB/s on a sixteen-lane (x16) configuration." A lot of technobabble, sure, but one thing's for sure: your next graphics card is bound to murder your current one if paired with a PCIe 3.0 motherboard.
PCI-SIG® Releases PCI Express® 3.0 SPECIFICATION
PCIe® 3.0 specification doubles bandwidth over previous generations
BEAVERTON, Ore. – November 18, 2010 – PCI-SIG®, the organization responsible for the widely adopted PCI Express® (PCIe®) industry-standard input/output (I/O) technology, today announced the availability of the PCIe Base 3.0 specification to its members. The PCIe 3.0 architecture is a low-cost, high-performance I/O technology that includes a new 128b/130b encoding scheme and a data rate of 8 gigatransfers per second (GT/s), doubling the interconnect bandwidth over the PCIe 2.0 specification. PCIe 3.0 technology also maintains backward compatibility with previous PCIe architectures and provides the optimum design point for high-volume platform I/O implementations across a wide range of topologies. Possible topologies include servers, workstations, desktop and mobile personal computers, embedded systems, peripheral devices and more.
"Each new version of the PCIe spec has doubled the bandwidth of the prior generation," said Nathan Brookwood, research fellow at Insight 64. "The latest group of PCIe architects and designers drove the standard forward while maintaining complete backward compatibility for Gen 1 and Gen 2 devices. Rarely has a standard advanced so non-disruptively through three major evolutionary cycles. The ability to pull this off demonstrates not only the ingenuity of the Gen 3 developers, but also the insight of those who defined the earlier versions in such an extensible manner."
The PCIe 3.0 specification extends the data rate to 8 GT/s in a manner compatible with the existing PCIe 1.x and 2.x specifications and products that support 2.5 and 5 GT/s signaling. This bit rate represents the most optimum tradeoff between manufacturability, cost, power, complexity and compatibility. Based on this data rate expansion, it is possible for products designed to the PCIe 3.0 architecture to achieve bandwidth near 1 gigabyte per second (GB/s) in one direction on a single-lane (x1) configuration and scale to an aggregate approaching 32 GB/s on a sixteen-lane (x16) configuration. The new 128b/130b encoding scheme also allows near 100% efficiency, offering a 25% efficiency increase for 8 GT/s as compared to the 8b/10b efficiency of previous versions, which enables the doubled bandwidth.
"The PCI-SIG remains dedicated to I/O innovation and we are proud to release the PCIe 3.0 specification to our members," said Al Yanes, PCI-SIG chairman and president. "The PCIe 3.0 architecture details significant improvements over our two previous PCIe specifications, providing our members with the performance and functionality they need to continue to be innovators in their fields."
This evolutionary specification integrates a number of enhancements to the protocol and software layers of the architecture. These enhancements range in scope from data reuse hints, atomic operations, dynamic power adjustment mechanisms, latency tolerance reporting, loose transaction ordering, I/O page faults, BAR resizing and many more extensions in support of platform energy efficiency, software model flexibility and architectural scalability.
The PCIe Base 3.0 specification is available for member download at http://www.pcisig.com/specifications/pciexpress/base3/.