A longstanding computing platform such as VME and the concept of a modernized battlefield may - at least initially - seem to be at odds with each other from a designer's perspective. Modernization however, means different things to different applications, and VME is holding its own depending on what level of performance, I/O and ruggedness designers need to address in evolving military applications.
Platforms such as VPX are picking up the slack " not replacing VME but rather offering options for rugged, high bandwidth processing that are keeping performance, budgets and development time intact.
VME's principal role in military design has been steadfast for more than 25 years, resulting from its adaptability, simple maintenance and rugged performance. But growth and change are constants, and military initiatives such as Warfare Information Network Tactical (WIN-T), Future Combat Systems and Joint Tactical Radio System (JTRS) have challenged VME's ability to accommodate the bandwidth-intensive communications and computing that has become common among network-centric military applications.
VME and VPX Complement, Not Compete
VME was one of the first open standards, bringing relief from the designer's most significant headache of dealing with proprietary operating systems and computing architectures.
At the time, the VMEbus architecture provided high bus bandwidth and a backplane that offered users easier maintenance and improved configuration flexibility. Designers welcomed its optimization for real-time computing, as it featured a 32-bit addressing and data path and highly ruggedized connector.
Continued evolution of military systems and their need for increased performance, I/O and ruggedness drove the development of VME64X. This became the new standard and effectively demonstrated the adaptability of the VME platform.
VME64X supported a 64-bit bus plus I/O features that included an additional backplane connector with 95 more pins and rear I/O capabilities. These new I/O features may have extended the life of VME, but since the accompanying connector technology changed very little, the issue of handling increased signal rates was still not solved.
CompactPCI gained similar popularity in military applications, because it answered additional I/O requirements with its own high-density connector solution. Many CompactPCI boards incorporate HSHM, or High Speed HM, connectors that include high-speed signals with backward compatibility. Even so, CompactPCI's connectors still are unable to address the differential signal performance required by certain real-time and mission-critical military applications.
More on VPX and Its Sister Platform, VXS
Many military systems began to integrate high-speed communications such as 10 gigabit Ethernet (GbE), RapidIO and PCI Express " moving a significantly greater quantity of data, and moving it too fast for VME connectors.
For example, with higher resolution HDTV video becoming a requirement for military imaging applications, 60 Hz frame rates rather than 30 Hz frame rates, are required. Military designers really needed to answer this issue with newer computing standards for high-speed serial communications.
Enter VPX, also known as VITA 46, spurred by this need for backplane, signal speed and I/O technology that could take today's demanding military systems into the future.
Before defining VPX however, VITA, the VME International Trade Association, specified the VITA 41 standard as an interim step. VITA 41 became known as VXS, addressing the need for I/O with a high speed differential connector in place of the P-Zero connector on VME64X, supporting PCI Express, Serial Rapid I/O and GbE in the backplane.
And VXS's access to serial switched fabrics is giving the platform a welcome home in software-defined radio applications. One key downside is that VXS requires a new or custom backplane.
It also actually has a lower pin count than VME64X because it replaces its center connector with a differential one. Field programmable gate array (FPGA)-based boards are driving the popularity of VXS, because their high frequency signaling is too high to run over standard VME connectors.
In contrast, VPX was developed to consider future application requirements. VPX lets designers use mixed backplanes, or backplanes with both legacy VME and VPX slots, so the most current connector, bus and serial fabric technologies can integrate into a VME solution.
Designers using a VPX-based board will also require a new backplane, but will be building a computing solution for high bandwidth, I/O intensive military applications in the process.
High speed radar signaling systems, real-time video processing systems such as UAVs or other video surveillance applications - or even new missile launching systems that are capitalizing on 1080 pixel video for the most accurate imaging and targeting - are all very likely environments for VPX.
On its own, VPX gives designers uniquely powerful and rugged performance for real-time military computing. And by integrating VPX into legacy VME platforms, designers have a path to retain the best of VME and incorporate significantly higher throughput.