Industry experts have predicted the demise of VME for years now, but the popular bus and board architecture standard refuses to die, and for good reason; it is still highly reliable for mission-critical embedded systems. It also enjoys a huge installed base of military systems supported by a broad and experienced ecosystem of suppliers. That is why designers of many legacy military programs choose to keep VME when upgrading or refreshing established systems. Tightening budgets and sequestration are also factors, as the expense of replacing existing VME chassis, I/O cards, and software makes it unthinkable to change to other architectures in many large programs.
The VME standard has kept its winning position in hundreds of defense program applications due to suppliers continually making bandwidth, connector, and I/O enhancements. Upgraded features and functionality keep VME a contender for event-based command and control systems, as well as help successfully satisfy the demanding requirements for signal-processing radar, sonar, and other intelligence, surveillance, and reconnaissance (ISR) applications.
However, VME’s throughput performance limitations present a hang-up for developers. Furthermore, bridging or interface device obsolescence affects the long-term life of VME, as evidenced by the recent end-of-life (EOL) notice of the popular TSI148 bridge chip.
These issues still do not dissuade OEMs, as the costs and familiarity in moving away from VME incentivize defense contractors to seek out cost-effective solutions to maintain this important and trusted technology investment. VME-based systems can remain viable with strategic embedded computing platforms that continue to evolve by integrating new disruptive technologies, enabling military developers to count on VME for many years to come.
Ways to keep VME relevant
Military applications developers must meet various requirements to keep VME-based systems relevant. These include building confidence in the processor migration for VME, extending I/O capabilities on the backplane, and offering the ability to support high bandwidth.
Effective migration strategies enable enhanced functionality
The latest COTS 6U VME SBCs provide an effective PowerPC and x86 processor migration strategy. These SBCs maintain a true bridge between PowerPC and x86, allowing designers to use the same mezzanine carrier, rear transition module, and front-panel I/O. They ensure pin-out compatibility on the backplane between board generations, and even across processor architecture families between PowerPC and x86. For instance, systems can transition from PowerPC to x86 architectures by implementing a current 6U VME board that integrates the latest Intel Core i5/i7 processors. This not only provides the flexibility to accommodate different CPU architectures, but also cuts down on development time while helping meet time-to-deployment goals.
One example of this type of 6U VME SBC is the Kontron VM6050 (Figure 1), which is fully compatible with all Kontron 6U VME products and thus enables OEMs to leverage x86 computing and graphics performance in existing designs based on the current line of either Intel or PowerPC VME SBCs without adjustments to the backplane. Demanding graphics applications such as those found in command and control centers or sophisticated military surveillance applications benefit from the VM6050’s Open GL 2.1 support and accelerated DirectX 10 capabilities to achieve enhanced and faster visual display capabilities on up to two monitors.
Utilizing FPGA technology
Traditionally, VME systems’ front-panel I/O was fixed to 3U or 6U form factor card functionality or had to be configured with PMC or XMC modules. Today, FPGA technology keeps PCI-to-VME bridging immune to silicon obsolescence in an era when suppliers are already issuing notices for legacy VME bridge chips. With the disappearance of PMCs, FPGA-based I/O solutions extend the life of I/O for years in existing embedded computers by employing an I/O mezzanine module with connection to an FPGA or other device with reconfigurable I/O capability.
For example, various VME applications can gain I/O control by implementing an XMC approach Kontron has developed wherein the XMC is separated into two components: an FPGA with PCI Express (PCIe) interface and the I/O with signal conditioning and custom connectors. This allows most of the legacy I/O mezzanines to be replaced with future-proof FPGA technology. This standards-based XMC approach uses VITA 57 to support the modular feature set at the software, hardware, and system level.
This approach utilizes a low-profile design that can be implemented on a variety of industry-standard VME computing boards and platforms. Once the feature is coded in FPGA language, it can be implemented on virtually any device specified, thereby overcoming the worry of obsolescence from currently used ASIC VME bridging chips. New high-speed connectors for I/O mezzanine modules support up to 10 Gbps transmission as well as single-ended and differential signaling up to 2 Gbps.
VME designs can leverage highly adaptable feature options that previously were restricted due to lack of interface or I/O support with the latest x86-based embedded computing platforms combined with FPGAs. Combined VME/FPGA solutions bring collective advantages that help reduce bill of material (BOM) costs while maintaining long-term legacy interface availability and matching current and future I/O needs. These new solutions provide an effective bridge that gives developers access to all the latest integrated processor features such as virtualization, hyper-threading, and graphics acceleration, adding new vitality and needed functionality to programs earmarked for upgrade or refresh. The FPGA solution enables designers to replace legacy or obsolete I/O and still maintain system integrity. This might require some initial software development if an existing IP core solution is not available. This is a significant advancement in bridging newer technologies with older systems implemented in the military market.
Support for high-bandwidth backplane evolution
A valuable use case is demonstrated by employing an SBC connection to PMC/XMC carriers to eliminate PCI bottlenecks. Because connection to multiple I/O interfaces calls for more bandwidth than VME or PCI buses can provide, this use case utilizes PCIe to supply the additional bandwidth.
PCIe offers transfer rates of 2.5 GBps routed through the VME64x backplane. Applications can be designed with one or two PMC/XMC carriers that allow the PCIe bandwidth between the SBC and the carriers to be far greater than the parallel PCI needed by legacy PMCs. Utilizing PMC/XMC modules plugged directly onto the SBC or carrier, a VME I/O subsystem high-bandwidth connection can be implemented with a modern VPX computing core. Then, using a UHS P0 connector to support PCIe signals enables a high-speed connection to the higher-performance VME processor board over the existing backplane and links VME-based SBCs with PMC/XMC mezzanine carriers.
Still going strong
VME still has a vital and useful role in military systems, and with embedded computing advances, it will remain a cost-effective solution for many more years. Evidenced by the standard’s huge installed base that calls for developers to maintain VME backplane compatibility, and that many of these systems do not have a requirement for higher data rate needs, it does not make financial sense to replace these systems.
VME remains a strong contender that provides repeated enhancements to bandwidth, expanded I/O options, and connectors, and continually evolves to support the latest PowerPC, x86, and FPGA processor architectures. These advancements translate into reduce costs and bring time-to-deployment benefits, making migration to a higher-performance VME solution a more attractive option than implementing a whole new computing platform. In fact, the number of VME-based systems in use today on ships and aircraft that could upgrade by simply changing out the board is most likely increasing. VME suppliers have found ways to extend its use implementing new technologies that eliminate the fear of bridge device obsolescence. In the past 15 years, Kontron has deployed many boards that use the company’s own FPGA-based PCI/VME bridge technology named ALMA so VME customers are not affected by EOL.
VME solutions continue to demonstrate their worth and staying power in many high-profile programs, including the missile launch control application on Triton submarines. As military systems continue to evolve, computing suppliers will fully understand the critical need to support their dynamic data processing and I/O requirements that don’t always call for the latest technologies with faster performance and higher bandwidth. Simplified tech-refresh strategies using 6U SBCs allow older processor cards to be replaced with the latest x86 or PowerPC processors and enable outdated PMC/XMC mezzanine modules to be exchanged all while maintaining VMEbus backplane compatibility.