Opening up new opportunities - Backplanes & Boards

Like any another technology, VME has continued to evolve since its introduction in the early 1980s. Originally featuring a 16bit data bus and capable of handling 80Mbyte/s, VME has evolved to its current 64bit incarnation. Today, the 2eSST approach supports 64bit parallel data transfers with bandwidths of up to 320Mbyte/s. But despite these developments, VME can't meet the requirements of some users as processors become more complex and data transfer rates continue to boom. So VITA – the VME International Trade Association –moved the technology on with the development of VPX. This broadly defined format is intended to allow the creation of a switch fabric within 3U and 6U blades. Within VPX is OpenVPX, a framework that defines system level VPX interoperability for multivendor, multimodule integrated system environments. This is an important consideration as the VME world has prided itself on the ability for boards from suppliers A, B and C to plug into a backplane from Supplier D. The OpenVPX framework defines clear interoperability points necessary for integration between module to module, module to backplane and chassis. However, OpenVPX recommends – but does not specify – systems to assist in the evaluation, prototype and development of VPX systems. OpenVPX, says VITA, will evolve and include new fabric, connector and system technology as newer standards are defined. However, OpenVPX is still trying to find some kind of common ground between suppliers. Dave Martin, head of sales and marketing for Elma Electronic UK, said: "There will continue to be amendments to the standard. It's definitely evolving, but it will probably be another year before it settles down." Historically, VME has been the technology of choice for military and aerospace applications – NASA's Mars Rovers feature VME card cages, selected for their ruggedness. But recently the The US Department of Defense and other users are looking for better open standards and interoperability. VITA notes that, while the VPX specifications have been focused at the board level, there is a need to consider system level requirements in order to improve interoperability and reduce customisation, testing, cost and risk. This is where OpenVPX comes in; the specification defines an architecture framework that manages and constrains module and backplane designs, including defining pin outs, and sets interoperability points within VPX while maintaining full compliance with VPX. Martin noted: "OpenVPX is the name for VITA 65, a document which serves as the umbrella specification for all the VPX related standards – VITA 46 (VPX), VITA 48 (REDI) and others being developed, such as VITA 62, 66, 67, and 68. It differs from other proposed standards in that it adds utility signals and specifies voltages for the 3U and 6U formats, while also creating a formal nomenclature for describing implementations." In terms of performance, VPX allows designers to create systems with bandwidths of up to 6.125Gbit/s per pipe, based on current technologies. Network performance can exceed that of Ethernet (10Gbit/s). Other serial switched fabrics are supported, including PCI-Express and Serial Rapid IO. Martin added: "The architecture enables this level of performance by putting different tasks onto different planes. For example, management, control, network and bus functions are each on their own plane, allowing greater control over system performance." GE Intelligent Platforms and Curtiss Wright Embedded Controls are amongst those companies developing OpenVPX compliant boards. GE has recently launched the SBC312, a 3U board featuring an eight core version of Freescale's QorIQ P4080 processor. Rob McKeel, the company's president, military and aerospace, said: "For new applications, it supports the development of very compact, high throughput solutions with optimum performance/watt characteristics." Curtiss Wright, meanwhile, is taking the 6U route is with the CHAMP-FX3. This OpenVPX form factor module houses two Xilinx Virtex-6 fpgas, along with a Freescale Power Architecture based processor. Curtiss Wright envisages the board being used in 'challenging embedded high performance digital signal and image processing applications'. Recognising the need for high speed connectivity and for flexibility, the OpenVPX specification describes a number of 'pipes', or bidirectional links. At the lowest level, an ultra thin pipe is one bidirectional link. A thin pipe is two bidirectional links, while a fat pipe comprises four such links. Interoperability is the goal with OpenVPX and it should allow users to mix and match boards from a range of suppliers in order to create the functionality they require. "This approach to the architecture tends to support a system level approach," said Martin,"unlike CompactPCI, for example." The approach is beginning to work. A recent press briefing was attended by 16 of the 32 members of the VPX Marketing Alliance, all of whom have products available to support the specification. According to Martin, there are now more than 100 products on the market. Elma is fully involved in the development of the specification. "We currently offer about six different backplane profiles, along with development and deployment boxes and a host of boards from our storage product line and from industry partners," Martin noted. "Elma is positioned to offer a range of system solutions based on interoperable products and to deal with the types of complex request at low to mid range volumes that will likely be typical of VPX applications." So who will make the most use of OpenVPX products? According to Martin, it will be the military. "In the UK, most of our business comes from the military and they love it. But in terms of new applications, it's probably too early; even in the US market." The attraction comes not only through the communications abilities, but also through the form factor. "It allows users to get more processing power into a smaller package," Martin noted. "Designers can now achieve in a 3U format what they used to need 6U for and the system can also be deployed in 'nastier' environments." That reference to the environment is underpinned by the nature of the connectors specified for OpenVPX. "They make it inherently rugged," Martin opined, "and more rugged than micro TCA, for example." OpenVPX still needs to settle down. "It is meant to be interoperable," Martin noted, "and any board is supposed to plug into any backplane. But that's not the case today. In another year, it will be. "Standardising the backplane, for example, is difficult. When you talk to board manufacturers, each has a different idea about what they want. But a lot of Elma's business is custom backplanes so, to some extent, the more customisation the better!" One thing of which Martin is fairly sure is that OpenVPX is an integration environment. "It's all about Level 4 system integration," said Martin. Level 4 integration involves loading active boards, disks, other devices and software into a chassis, then testing the system for functionality, performance, safety and proper configuration. "It's unlikely we'll sell many chassis with a backplane and nothing in them. Customers will want systems in which everything works with everything else," he concluded.