A new VITA specification is set to enable rugged systems the size of a Rubik's Cube

4 mins read

Since its early days, components for VME and similar systems have been measured in terms of units – or U. At the larger end of the scale, boards have been manufactured in the 6U format – measuring 19 x 10.5 x 19.5in. Many of these products were used in military applications and, at the time, size was not a major issue. In fact, the combination of ruggedness and ease of maintenance was more important.

However, over the last few years, customers for such products have started to focus on SWaP – size, weight and power. Looking with some degree of envy at small form factors such as NanoETX, industry association VITA put in motion efforts to produce a small, rugged form factor that met SWaP requirements and the result is VITA 74.

Jerry Gipper, executive director of VITA, provided some context. "VITA has a long history with small form factor boards, beginning with the original 3U VMEbus; deemed necessary to address the needs of space limited industrial applications. Many early VMEbus products were 3U, but there was limited backplane I/O so, over time, 6U gained the larger market share.

"The VPX concept was proposed in 2004. It also had 3U and 6U form factors, but the use of serial switched fabrics in a much higher pin count connector – up to 280 pins in 3U – made the smaller board size very popular. As in the early years of VMEbus, the 3U format gained many early design wins."

But, with demand growing for smaller, high performance systems and the development of processors with integrated memory controllers, I/O and serial fabrics such as Ethernet and PCI Express, the opportunity has opened up to drive innovation. "Standards developers had rugged and mobile applications in mind from the start," Gipper continued. "They are taking into consideration various cooling strategies, from convection to conduction, focusing on lower module mass and keeping performance and serviceability in the forefront."

The VITA 74 specification is being promoted by the VNX Marketing Alliance – a group of interested parties formed within VITA. It says VITA 74 was developed specifically to address the needs of architects designing small embedded computing platforms for rugged operating environments.

Gipper noted: "The inspiration for VITA 74 came from reviewing existing COM standards, including nanoETXexpress for miniature CPU modules, existing VITA standards for VPX and FMC and the smaller sized and target price point PC/104 modules. The requirement from the user community was for a price sensitive, standards based approach for small conduction cooled systems in applications where SWaP is important.

"These applications include aerospace, unmanned vehicles, robotics, man wearable systems and energy exploration. Many of these applications require electronic subsystems that are both rugged and mobile or portable – something that is impossible with traditional 3U and 6U backplane based systems."

And while the goal might not be achieved immediately, the VITA 74 standard could result in boards the size of a credit card, standalone computers the size of a pack of cards and systems the size of a Rubik's Cube – but with a level of performance similar to that from a traditional system.

Gipper provided more insight. "The key driver for VITA 74 has been the SWaP restrictions of many systems – especially air and mobile. The modules will enable systems to be built that are much smaller than today's 3U or 6U form factors."

The Alliance notes that VITA 74 defines the mechanical and electrical specifications required to implement a small form factor system. The specification addresses a need for a standardised approach to small scale systems and encourages multiple vendors to supply components to be used in small systems at various levels, including modules, backplanes, enclosures and integrated systems.

Recognising that much work has been done in the past in developing previous VITA specifications, VITA 74 development has been based on the VITA 46 specification. The specification, says the Alliance, takes many of the conventions and signal definitions, translating them into a small form factor. It adopts the signal mappings – signalling is said to be similar to VITA 46 (VPX) and VITA 65 (OpenVPX) – whilst introducing a new high speed low cost connector and reducing the number of serial fabric options.

VITA 74 supports two serial fabrics – Ethernet and PCI Express – and a single CPU root node has been adopted in order to keep the system as simple to implement as possible.

The base standard gives details on the mechanical implementation of the system plug in modules. Two types are defined: 19mm and 12.5mm. Each type addresses a different set of functions.

The 12.5mm format, which suits single base cards, features a four row connector with 200pins and is likely to be used for peripherals such as I/O and storage.

The 19mm option is more capable, accepting a base card as well as a nanoETXexpress sized mezzanine card. This requires an eight row connector with 400pins and is likely to be used for applications such as single board computers, smart displays and software defined radio.

Themis Computer, a founder member of the VNX Marketing Alliance, has developed the NanoATR system, based on VITA 74. This features an Intel Atom or AMD Fusion processor in a small, lightweight enclosure and is said to an ideal solution for rugged commercial and military field applications.

It draws on Themis' thermal and kinetic management design expertise, boasting a fully sealed, finned, hardened aluminium conduction cooled chassis which can accommodate two 19mm and two 12.5mm modules. There is a rear mounted storage slot, an I/O transition panel and a power supply unit. A standard front panel features circular MIL connectors, but specific customer requirements can be met.

While Themis has produced a device with four modules, VITA 74 doesn't specify a backplane implementation, so it is possible that systems could be created with other combinations. Neither is there any specification of the enclosure and this aspect is being left to individual vendors.

Gipper said the specification is in VITA Trial Use status and publically available. "This means it is complete and solid enough to build modules, but changes may be made in the future based on the results of early adopter users," he cautioned. "The VNX community is currently preparing a list of additions and enhancements to the specification before the trial use period ends in late 2016. At that time, the VITA process requires the working group to complete the specification and move to the ratification stage."

VITA 74, meanwhile, is evolving alongside two similar specifications – VITA 73 and VITA 75. "VITA 73 and VITA 74 are similar in that they define modules that are nearly the same size," Gipper explained, "while VITA 75 defines enclosures and types of connector. So VITA 73, VITA 74, and 3U VPX could all be modules within a VITA 75 enclosure."

What are the market prospects for VITA 74? "The VNX Marketing Alliance has not released any predictions on market size yet," Gipper concluded. "But if I had to make my own projection, I see the market being worth more than $50million a year in a couple of years as early adopters deploy systems."