The new VITA 100 suite of standards is shaping up to be an interesting display of computing system standards development. Built from years of experience, stemming from VME and OpenVPX, VITA 100 is drawing on the best of these earlier standards to craft a new standard that will enable suppliers and integrators to hit the ground running as soon as the documents are released.

There is one technical element of VITA 100 that appears unusual and perhaps even contrary to a standard that is trying to establish a firm market with interoperability as a prime motivation by minimizing the number of variations. That element is the 4U form factor.

4U accommodates modern embedded designs

At first glance, some may consider 4U an odd choice for inclusion in the standard. It’s larger than the more common 3U form factor that currently dominates the OpenVPX (and Sensor Open Systems Architecture/SOSA) market, but is still notably smaller than the venerable 6U form factor. Looking at the issue from a distance, this additional form factor might seem to simply fragment the market. However, there are good reasons why 4U has been proposed and why it may come to dominate the high-performance embedded computing market.

One significant trend that is clearly emerging in embedded computing – and is likely here to stay – is an increase in component size. Higher-end CPUs, GPUs, and FPGAs [central processing units, graphics processing units, and field-programmable gate arrays] are growing larger, especially with the explosive adoption of system-on-chip (SoC) designs. These highly desirable components and their support chips are already exceeding the surface area that a 3U board can supply, and the problem is only likely to get worse.

Take, for instance, the primary component side of the PCB [printed circuit board] on a 3U conduction-cooled OpenVPX card, the only side available for a processor due to component height and cooling restrictions. It offers a maximum of 11,907.82 mm² of component surface area. (In reality, the usable area is even a bit less due to keep-out regions and other limitations). An Intel high-core-count (HCC) Ice Lake-D processor, which is a popular number cruncher in modern VPX-based computing, comes in at a 52.5 mm by 45 mm (2,362.5 mm²) package, or around 20% of the surface area of the primary component area noted above.

Add component clearance area around that, with two or (preferably) four banks of DDR4 memories, Ethernet transceivers, power supplies that can take up to a third of the board area, plus other assorted necessary components – not to mention space for routing circuits – and component space is quickly exhausted.

GPUs and FPGAs are bad or worse, with the latest NVIDIA Blackwell GB202 sporting a 24.1 mm by 31.6 mm (762.5 mm²) package, and the largest Xilinx Virtex Ultrascale+ at a whopping 65 mm by 65 mm (4,225 mm²)! As a result, vendors must sometimes sacrifice features that otherwise might be desirable, due to limitations of the existing system infrastructure.

What 4U brings to the table

Enter VITA 100’s 4U form factor. From the start, the designer picks up at least one-third more board space (probably more due to keep-out and cooling structure space), leaving a lot more room for components and routing. Thus, the designer is less likely to have to make painful feature cuts to fit these jumbo components.

There’s another reason why 4U may be an attractive choice for these higher-performance components and systems. 3U and 6U VITA 100 boards are constrained by the desire to be physically compatible with OpenVPX board geometries – not the connectors, but the cooling rail geometries, board pitch, etc. This layout enables 3U and 6U VITA 100 systems to fit into existing OpenVPX-sized “holes” on platforms. As a result, the cooling paths for 3U and 6U VITA 100 will have generally the same thermal performance as their OpenVPX forebears.

4U does not have this constraint. The VITA 100 standard’s Working Group is actually free to adjust things to make cooling more efficient. While this factor has not yet been decided upon within the standard, it opens the door to some intriguing design possibilities.

Shaping next-gen embedded systems

VITA 100 is turning out to be an ideal platform for next-generation high performance embedded computing. Not only does it provide an alternative form factor to accommodate higher-end components, it offers a fourfold improvement in bandwidth over OpenVPX, while doubling the number of pins available to the backplane, and carries forward many of the great system features found in current OpenVPX systems.

Additionally, as it is a system standard unburdened by the need to support existing products like the situation VITA 65 had to contend with, VITA 100 will likely be a much more-tightly written standard, with less interoperability-killing custom features, such as vendor-defined pins. This new 4U form factor could prove to be quite a game-changer in next-generation embedded computing.

Mark Littlefield is Director, System Products for Elma Electronic.

Elma Electronic · https://www.elma.com/en