The File - Oct 1, 2008 - (Page 5)

Trends PCIe expands interconnect potential for next-gen systems By Krishna Mallampati Senior Product Marketing Manager PLX Technology PCI Express (PCIe) has emerged as the interconnect standard in the control plane and is now making inroads into the data plane segment of the telecommunication market. With an expanding number of processors from vendors such as Freescale, AMCC, Cavium, RMI, LSI (Tarari Content Processors), Tilera and Clearspeed providing several PCIe ports, the PCIe interface has successfully penetrated the telecommunication, embedded and security markets. New processors from these and other vendors are being designed with native PCIe interfaces—in some instances, with multiple PCIe interfaces, depending on the target market segment. The port width of each PCIe interface depends on the applications the processor serves. According to the Linley Group, the global PCIe interconnect (switches and bridges) market is expected to nearly quadruple in the coming few years—growing from Rs.236.56 crore ($55 million) in 2007 to Rs.838.71 crore ($195 million) in 2011. Analysts see India’s communications market segment contributing to that growth. With one or more native PCIe interfaces, these processors still do not have sufficient PCIe ports to connect all the other devices present on the board—devices such as ASICs, FPGAs, Fibre Channel end-points and Ethernet end-points. Designers who need to connect several devices Discuss Infiniband will ride on PCIe success PCIe data rates on board provide Infiniband an able partner. Will PCIe success drive Infiniband takeup? Discuss… to the processors need a PCIe switch to fan-out PCIe connectivity from the processor. Different requirements The requirements for PCIe switches in the telecommunication, embedded and security markets (to provide fan-out) are dramatically different from those for the graphics, servers and storage markets. The control plane telecom market, for example, calls for switches with a greater number of ports with one lane per port, whereas graphics cards, servers and storage systems need fewer ports with larger number of lanes per port. An ideal PCIe switch for telecommunications will have an equal number of lanes and ports. The worldwide design community has settled at the sweetspot of 16-lane and 16-port switches for telecommunications, which is due to the fact that the control plane has a large number of end-points that need to be connected to the processor to aggregate all control functions, such as statistics gathering and configuration updates. A PCIe switch with 16 lanes and 16 ports meets the needs of a large number of telecommunications systems. Another unique need in telecommunications systems is traffic-priority differentiation—high priority and low priority. This can be accomplished by using a PCIe switch with two virtual channels (VCs). VC 1 can be assigned to high-priority traffic, while VC 2 can be assigned to low-priority traffic, thereby providing a range of priorities within the system. A third and equally significant requirement in telecommunications systems is for a Mallampati: For systems being introduced in 2009 and beyond, a Gen 2 PCIe switch will be needed to build these next-generation systems PCIe switch to support spread spectrum clock (SSC) isolation, whereby the switch should be able to operate in two different clock domains. This is significant because in telecommunications, PCIe is applied across the backplane for long distances and users may need cables and re-drivers, requiring the switch to operate in two different clock domains. Backplane needs A 16-card system with one controller card and 15 line cards needs to connect all these cards on the backplane. A 16lane, 16-port PCIe switch is typically used on the control plane. The PCIe switch routes all the control functions, both within the line card and between the controller card and multiple line cards. In figure 1, the control plane goes across the backplane with PCIe connecting the two. The non-transparent (NT) port of the PCIe switch on the line cards isolates the local processor from the control processor on the controller card to enable proper enumeration and isolation. Since the same PCIe switch supports multiple configurations—a 16-lane, 16-port configuration and a 16-lane, 4-port configuration—designers need not worry about using different switches for different configuracontinued on page Figure 1: A 16-lane, 16-port PCIe switch in a control plane. EE Times-India | October 1-15, 2008 | www.eetindia.com http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/PCIe.HTM?ClickFromNewsletter_081001 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/FPGA.HTM?ClickFromNewsletter_081001 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/Fibre Channel.HTM?ClickFromNewsletter_081001 http://www.eetindia.co.in/SEARCH/SUMMARY/technical-articles/Fibre Channel.HTM?ClickFromNewsletter_081001 http://forum.eetindia.co.in/FORUM_POST_1000039250_1200080782_0.HTM?ClickFromNewsletter_081001 http://forum.eetindia.co.in/FORUM_POST_1000039250_1200080782_0.HTM?ClickFromNewsletter_081001 http://www.eetindia.com/STATIC/REDIRECT/Newsletter_081001_EETI02.htm?ClickFromNewsletter_081001

Table of Contents for the Digital Edition of The File - Oct 1, 2008

EETimes India - October 8, 2008
National Semiconductor
Tech Insights
Trends
Cadence
Texas Instruments
Fine-tuning RF Platform Shrinks Design Time
DigiKey
Mobile WiMAX Enables IP Convergence

The File - Oct 1, 2008