The Future of VITA-based SFF and Mezzanine Boards



Experts weigh in on VITA and related standards such as CompactPCI, discuss the future of modular and small form factor (SFF) VITA-based boards, and take sides on the buzz around PCI Express versus InfiniBand.

Despite VME’s and VPX’s longstanding reputation for heavy-duty applications, a range of modular and small form factor VITA standards (VITA 59, VITA 73, VITA 74, VITA 75) are grabbing attention. Our experts—Richard Kirk, product manager, military/aerospace single board computers, GE Intelligent Platforms; Nigel Forrester, product marketing manager, Artesyn Embedded Technologies; and Barbara Schmitz, CMO, MEN Mikro—provide a well-rounded view of the opportunities and challenges as VITA standards shrink. But small isn’t the whole story, and our panel also addresses what’s happening in high-performance computing interconnects and the roles of PCIe and InfiniBand in these demanding applications.


EECatalog: 3U VPX vs 3U CompactPCI—similar, but different. How close are they, and why use one over the other?

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Richard Kirk, GE Intelligent Platforms: 3U VPX and 3U CPCI cards tend to have similar capabilities in all but the backplane interface, where VPX offers much higher bandwidth capability. So for mil/aero, 3U VPX is seen as the natural upgrade from 3U CPCI when the highest possible performance is required. CPCI Serial also offers upgraded backplane bandwidth, but with mil/aero vendors focusing on VPX, there is a much wider choice of suitable payload cards, backplanes and infrastructure to build complete solutions from. Also, 3U VPX is now offering genuine opportunities to improve SWaP when upgrading much larger systems previously focused on 6U VME and CPCI. With much improved processing and backplane performance available on 3U VPX, large multiboard 6U applications can now be dramatically “shrunk.”

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Nigel Forrester, Artesyn Embedded Technologies: They are both 3U and so physically they can accommodate similar functionality. The original 3U CPCI specification was bus-based but the more recent CPCI Serial has similar serial fabric capability to VPX. The main difference lies in the application/market focus and the take-up: 3U VPX was designed specifically for military rugged applications whereas CPCI was originally driven by telecommunications opportunities, but over time has been used in other applications including industrial control. Since the OpenVPX standard was ratified, it has become widely supported with over 30 manufacturers advertising products, compared to CPCI Serial which is only available from a handful of vendors.

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Barbara Schmitz, MEN Mikro: Based on proven 19-inch mechanics, some of the important functions for safety and reliability—such as hot-plug/hot-swap or a good heat dissipation including conductive cooling—do not need to be reinvented. Modularity and robustness cannot be specified as an afterthought, as can be seen in standards such as ATCA and microTCA, which mandate these attributes. With the recently introduced CompactPCI Serial standard, which takes CompactPCI to modern serial point-to-point connections, both the VPX and current CompactPCI standards give good reasons to employ robustness in demanding, data-hungry applications.

VPX (as in VXS and VME before) has a long history in military applications and also in the avionics and aerospace industry, so products are manifold and proven. Also VPX offers special interconnects such as Serial RapidIO or Aurora. But there a many benefits of CompactPCI Serial in harsh applications as well: delivering a full mesh on the backplane, it doesn’t need any switches or bridges, since it has the same functions as the VPX connector but is less expensive. CompactPCI Serial uses a strictly standardized pin assignment that is compatible to its predecessor, CompactPCI (using CompactPCI PlusIO in a hybrid system), and most applications can be built up of standard boards and backplanes at least for the most part; there are no or very small NRE costs. The high number of configurations in a VPX system could be cause for interoperability.


EECatalog: PCI Express Gen 3 promises more bandwidth and more lanes, but InfiniBand has taken the HPC/HPEC VME world by storm this year. What’s all the buzz about?

Kirk, GE Intelligent Platforms: InfiniBand offers great scalability and a well-established software ecosystem and is therefore ideal for extracting the highest performance from multi-node systems. For smaller systems, the fact that PCIe is ‘native’ in most devices means that it is a more obvious (power/space/cost effective) interconnect methodology than InfiniBand, which requires additional board space and power. Both ecosystems have a role to play across the spectrum of applications seen in mil/aero and both look to have a strong future.

Forrester, Artesyn Embedded Technologies: The buzz is all about using modern interfaces to increase bandwidth, and PCI Express and InfiniBand are largely complementary. PCI Express (PCIe) is used as a high-speed, point-to-point connection method for in-system use and benefits from widespread silicon support. Each PCIe generation offers increasing bandwidth per lane (Gen 1 was 250MB/s and now Gen 3 is 985MB/s) and it is common to use multiple lanes (x4, x8, x16) for high speed FPGA, GPGPU and CPU connectivity.

InfiniBand has migrated from an inter-system and system-I/O transport that typically uses SFP connectors which can be both copper and fiber. Fiber connectivity enables much longer distances and InfiniBand is more suitable than PCIe for distributed applications between supercomputer boxes and storage. As an example, a radar system might have a control processor linked by PCIe to a GPGPU and this box might be linked by InfiniBand to an offsite storage array. More recently, Infiniband along with or in place of 10/40GbE is increasingly being offered as a data plane fabric option in VPX and VXS HPC/HPEC for the connection of system computing elements, owing to its very high bandwidth, scalable intra-/inter-system capabilities and native RDMA support. RDMA is the basis for the Open Fabric Alliance software stacks used to develop HP[E]C applications, and has not been generally available for PCIe. PCIe continues to be the standard for expansion plane connectivity in VPX, and Gen 3 provides higher bandwidth with fewer lanes, important for 3U applications.


EECatalog: Migrating DSP applications from FPGAs and PowerPCs on VME to Intel’s latest Haswell (Core i7, Gen 4) processors—what are the issues, and where’s the software?

Kirk, GE Intelligent Platforms: We have seen many customers migrate applications from Power Architecture to Intel Architecture—specifically, from AltiVec code to SSE or AVX code. The methods employed depend on the nature of the code. The two types encountered most are library calls and C code with Intrinsics. In the case of the former, sometimes the library in use is available for both processors—as in the case of GE’s RSPL, or the open-standard VSIPL. Then all that is needed is a recompile and link against the new version of the library. If it is a library that is not available for Intel then some work is involved in the migration, but it is generally not onerous, often involving recasting one library call to another, either manually or via automated tools. For code using Intrinsics, Intel made an AltiVec.h file available that mapped AltiVec calls to SSE calls.


EECatalog: Are we headed towards more mezzanine card standards? Might there be a computer-on-module (COM, PICMG-like) trend in VITA’s future (think VITA 59, Rugged System on Module)?

Kirk, GE Intelligent Platforms: There is definitely interest from customers in computer-on- module/mezzanine concepts, whether it’s XMC or COM Express—or even something proprietary. The main perceived benefit is the concept that the CPU can be regularly upgraded without changing the rest of the system. In reality, mil/aero customers like the idea—but then each one wants something slightly different to the standard and also most don’t really want to change the CPU halfway through a program due to the costs of requalification. The worst possible scenario would be a proliferation of different mezzanine standards, as then even the concept of modularity and choice would be diminished.

Forrester, Artesyn Embedded Technologies: This and the following question are somewhat linked. VPX is very well-suited to modular systems, however even the smallest 3U VPX system is too big, heavy or high-performance for some applications. There are some applications where a custom carrier fitted with a single computer-on-module is sufficient, but there are inherent difficulties in this hybrid approach: modules from different manufacturers do not always work in the same way; cooling and ruggedization are tricky and there often needs to be direct engineering contact between the two groups to resolve development and deployment challenges. The mezzanine approach can be cost-effective and for this reason it is likely to become more attractive.

VITA 59 is an attempt to address COM thermal/mechanical issues. It initially meant to standardize the module/carrier signals around a new rugged connector, while also maintaining optional backward compatibility with COM Express. It has since become largely a rugged version of standard COM Express. Customers are already fielding COM Express-based designs with standard connectors and custom thermal solutions and carriers, so it remains to be seen whether VITA 59 will find adoption, versus continued DIY, or one of the SFF standards. The cost-effectiveness of any modular approach depends on the application’s requirements for scalability, vendor independence and technology insertion.

Schmitz, MEN Mikro: Modern embedded systems have high demands: powerful, flexible, cost-effective and a compact and maintenance-free design. This is where COMs come into play.

One of the most common standards for COMs on the market is PICMG COM Express, which provides a modern platform for different CPU architectures like x86, PowerPC or ARM, but is mainly developed for commercial applications with low thermal design, shock, vibration and EMC requirements.

For more rugged applications like rolling stock, avionics and military, the standard design of a COM Express module is not feasible, so the VITA 59 standard was developed to make COM Express ready for mission-critical and harsh environments. With VITA 59, it is quite easy to modify an existing COM Express module just by changing the mechanics and putting it into a conduction cooling frame.


EECatalog: VME, VPX, VXS are all targeted towards “critical systems,” yet smaller form factor (SFF) systems such as VITA 73 or VITA 74 are grabbing attention. Some of these SFFs are not designed to be as rugged and reliable as VME or VPX. What are the market trends? What are customers saying?

Kirk, GE Intelligent Platforms: Again there is some interest in VITA 73 and 74—but customers are generally nervous about adopting solutions which aren’t universally supported by the leading industry players. Those customers’ ideal situation would be a wide choice of suppliers, a wide choice of functional building blocks and a clear roadmap into the future. This hasn’t really happened yet so most SFF solutions are still using existing building blocks (COM Express, XMC, 3U CPCI, etc.) and the focus has been on making these as small as possible. It doesn’t seem like a clear SFF standard winner is likely to emerge in the near future, so the current situation look set to continue.

Forrester, Artesyn Embedded Technologies: Customers want everything: smallest size, weight and power; lowest cost; longest availability in the market; most choice. There is usually a compromise, and with three VITA SFF proposals (73, 74 and 75) driven by competitors, the vast majority of applications will stick with OpenVPX for now. In some respects, the smaller the system the easier it is to ruggedize, and so over time it is likely that a SFF format could provide equivalent capability to 3U VPX, however the major stumbling block today is the lack of industry coalescence behind a single standard. Until that happens the market will remain fragmented and 3U VPX will be the choice for most new military programs looking to use COTS products.


coupe_cherylCheryl Berglund Coupé is managing editor of EECatalog.com. Her articles have appeared in EE Times, Electronic Business, Microsoft Embedded Review and Windows Developer’s Journal and she has developed presentations for the Embedded Systems Conference and ICSPAT. She has held a variety of production, technical marketing and writing positions within technology companies and agencies in the Northwest.

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