VITA Small Form Factors
Several conditions have come together in recent years to drive innovation in even smaller form factors. First, the continued integration of processors to include memory controllers, I/O, and serial fabrics such as Ethernet and PCI Express; and second, a rapidly expanding market need for high-performance, small computing platforms for unmanned mobile vehicles. But new initiatives are different. Standards developers have had rugged and mobile applications in mind from the get-go. They are taking into consideration various cooling strategies from convection to conduction, focusing on lower module mass, and keeping performance and serviceability at the forefront.
VITA has a long history with small form factor boards, beginning with the original 3U VMEbus that was deemed necessary to address the needs of industrial applications that were space limited. Many early VMEbus products were 3U in size, but the major deficiency for these products was the limited availability of backplane I/O connections, so over time 6U gained the larger market share.
Fast-forward a few years to the switched fabric era of module interconnections. The VPX concept, proposed in 2004, also has 3U and 6U form factors defined in the specification. The use of serial switched fabrics in a much higher pin-count connector (up to 280 pins in 3U) make the smaller board size a very popular choice. As in the early years of VMEbus, the 3U size gained many early design wins.
VPX was driven by a need to develop a rugged form factor that utilized serial switched fabrics such as PCI Express, Ethernet, serial RapidIO, and InfiniBand for module interconnection. The original target market was High-Performance Embedded Computing (HPEC) for defense applications where Size, Weight, and Power (SWaP) was a major concern. The small 3U size is particularly suited for vehicular mobile platforms.
In rapid succession, three proposals for smaller form factors that all leverage work done on VPX began specification development under the VITA Standards Organization (VSO). The efforts at VITA are primarily focused on small form factor blades that require a backplane to interconnect modules.
VITA 73: Small Form Factor (SFF)
VITA 73 was conceived while searching for a solution to a Network Attached Storage (NAS) problem, when a 2.5" X-frame carrier for Solid-State Disks (SSDs) was determined to be an appropriate form factor for an embedded computing platform (Figure 1). VITA 73 provides a standard mechanical format with switched serial interconnects based on VPX, with specific concern taken to allow deployment in rugged environments. The working group developing the specification had several goals, with size and weight leading the list. The group also wanted to ensure that performance is maintained through the module interconnection scheme. At the same time, easy maintenance and no cables in the system drove many decision points.
The VITA 73 working group is nearing completion of the specification, and is preparing for “Draft Standard for Trial Use” status by the end of 2013. Evaluation modules are available from PCI-Systems.
VITA 74: Nano Small Form Factor (NSFF)
The inspiration for VITA 74 came from reviewing existing Computer-On-Module (COM) standards, including nanoETXexpress for miniature CPU modules, existing VITA standards for VPX and FPGA Mezzanine Cards (FMCs), and smaller, price-point targeted PC/104 modules. The targeted user community has a need for price-sensitive platforms with a standards-based approach for conduction-cooled systems. The working group – consisting of several merchant board manufacturers, system integrators, and defense prime contractors – drew from existing open standards to reduce risk and schedule.
The working group design goals are as follows:
- Boards the size of a credit card, including 12.5 mm and 19 mm modules (Figure 2)
- Stand-alone computers the size of a deck of cards
- Systems the size of a Rubik’s Cube
The VITA 74 working group is nearing completion of the specification, to be followed by balloting. The specification is on target to be publically available in early 2014. Modules and systems are available from Themis Computer and Creative Electronic Systems (CES).
VITA 75: Rugged Small Form Factor (RSFF)
VITA 75 is a “voice of the customer”-driven program. The scope of the VITA 75 project is broken down into modular subsystems that define the complete platform (Figure 3). The VITA 75 specification defines a box and external interfaces to that box, including the:
- VITA 75.0 Base Profile – Defines external dimensions and the envelope the subsystem must fit within. Its size is scalable.
- VITA 75.1x Front Panel Profile – Defines the power and signal interfaces that connect externally to the subsystem.
- VITA 75.2x Cooling and Mounting – Defines various cooling methods and the interface for cooling the subsystem.
- VITA 75.x Internals Structure – Defines types of modules that can be used within the Base Profile.
VITA 75 is a specification that defines a small form factor, box-level standard that is based heavily on customer demands. VITA 75 is most notably differentiated from the VITA 73 and VITA 74 initiatives in the fact that it focuses on the box in terms of both size and the level of ruggedization of the operating environment. The internal modules are yet to be defined, but could easily include VITA 73- or VITA 74-style modules.
The VITA 75 working group released several sub-profiles of the specification to “Draft Standard for Trial Use” status. The intent is to give manufacturers and users the opportunity to design, build, and use products, then provide feedback to the developers based on actual use.
VITA 59: Rugged COM Express
Added to the mix of small form factor projects is VITA’s Rugged COM Express standard. The COM Express specification was developed under the PCI Industrial Computer Manufacturers Group (PICMG); however, VITA members who were also PICMG members felt that the VSO was better equipped to help define a more rugged version of COM Express. The working group is now preparing to roll out a rugged version of COM Express by early 2014. Working together to combine the efforts of both organizations has greatly reduced the time to develop and complete this specification.
Shrinking size for a growing opportunity
We are only at the beginning of a wave of even smaller form factor products. By nature, electronic components want to become smaller and more functionally dense. Many small form factor Single Board Computers (SBCs) are competing for a share of a rapidly expanding market in many application spaces. We can only expect a similar trend to continue for interconnected boards.
VITA Standards Organization (VSO)