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Even the military is following the trend of consumer electronics—more functionality, smaller, less power and cheaper. The only problem is that the military can’t accept a “use it for 18 months then throw it away” policy. In decades past, every one of those goals was a compromise for the military—and cheaper was never able to become part of the consideration. Engineers had a limited amount of allowable space, weight and power to play with—which usually meant they had to compromise on any extra capability and performance.
Non-Developmental Items or COTS products found the majority of their home in existing platforms requiring upgrades or technology insertions. Having to go into existing platforms set the parameters of how much space, weight and power the upgrade was restricted to. Increased silicon performance and integration advancements meant a program could usually get the functionality needed while at the same time adhere to the durability requirements of the system and its constraints within the end platform.
Most systems—at least vetronic systems—use the ATR (Air Transportable Rack) as the common denominator for system envelope classification. These are defined as ATR-Long, ATR-Short, ½ ATR and ½ ATR-Short. This is similar in concept to the way the embedded board industry divides up bus board sizes: 9U, 6U and 3U. What’s happened recently is that, in some cases, the available system envelope within a platform has exceeded the space required to accomplish all the specifications of the upgrade. This results in upgraded ATR systems with empty board slots. And in some cases the ongoing advancements in silicon have brought the level of board integration to the point where an upgraded ATR system contains just one board providing all the processing upgrades and enhancements of the system it is replacing.
ATR systems evolved as containers around the necessity to internally interconnect different electronic modules/boards. In previous decades parallel bus technology was used as the interconnection; more recently, serial and serial/parallel bus technology have become the backbone of these systems. Multiple board systems also played into the military’s desire to have systems with a 20-year availability. Bus boards allowed for a fairy tale concept of having multiple vendors. These vendors could in theory provide similar substitute boards if a vendor could no longer provide a board—or if a vendor was acquired by another company and the product was discontinued.
The real truth is that if an element—such as a board—within a pre-integrated system has to be replaced with a board that isn’t a direct substitute, then the system needs to be requalified. And more than likely the application software also needs to be modified and then requalified. Any end-user or platform supplier will tell you, the last thing anyone wants to do is to get into the application software. That was what the multi-vendor fairy tale concept was intended to eliminate. Often times when a one to one board replacement isn’t possible, it justifies an entire pre-integrated system review. There was no fairy tale salvation and no insurance if a vendor or their product disappeared.
Even for the military, there will always be a demand for computing performance that’s higher than the current technology can provide. Today there are large high-performance systems using several xTCA and OpenVPX boards on one end of the spectrum and single board PC/104 or small proprietary systems on the other. As a result of silicon advancements, we’re now at the point where we’re seeing cases where a single computational element (small board or box) performs all the tasks necessary for a particular subsystem. In some respects these single element systems may actually fulfill some of the fairy tale concept. That’s because the application software in those systems has no need to consider the interplay between the elements within. Since there’s only one element, the software only needs to control signals in and out. The single element supplier—or replacement supplier—is responsible for everything going on inside. Now that may be wishful thinking, and the replacement vendor can’t always emulate previous system operation, but at least it makes sense in theory.
It does seem strange to be looking at a vehicle’s system bay and see a very small metal box in place of what was once a ½ ATR-Short system. Even stranger looking, that small box—only a fraction of the size of the ATR it replaced—sports what now looks like two oversized connectors going into it. New platforms, especially UAVs, are not constrained with the ATR legacy form factor and are taking full advantage of fully contained non-bused single supplier systems as they become available. Perhaps what is needed is a new envelope standard to replace the old ATR envelopes. And something with a little vision for the future wouldn’t hurt either. Now where’s that tooth fairy?
Great points, Pete! Take a look at the proposed VITA 74 spec and you may see that tooth fairy...:-)))