The little engine that could - and still does
The COM Express standard, or family of standards as it is sometimes described, is ten years old this year. COM Express has emerged as the most widely used small form factor for thousands of applications worldwide.
While hard numbers are difficult to get, COM Express vendors who exhibited last year at Embedded World, the largest embedded board and system show on Earth, generally agreed that the market at that time, about 18 months ago, was in excess of 2 million units annually representing about $400 million in revenue. With the intense interest in the Internet of Things (IoT) and the push to make everything from appliances to automobiles to municipal transportation and power systems “smart” and connected to each other and the Internet, that number will surely increase dramatically.
The COM Express standard defines a family of Computer On Module (COM) single-board computers appropriate for a wide range of commercial and mil/aero applications. It is designed to accommodate modern high-performance chipsets and serial signaling protocols, including PCI Express Gen 3, SATA, USB 3.0, and high-resolution video interfaces. It is entirely open, and anyone may build COM Express products without licenses or royalties.
COM Express not only provides high performance, it is unique in that it may be used in two ways:
1. As a standalone single-board computer
2. As a processor mezzanine that can be plugged onto a baseboard, or “carrier” board, that contains the user’s application-specific I/O
The mezzanine capability is enabled by two standardized connectors mounted on the bottom of the board that can plug onto a board below it. All versions have these two connectors, although there are slight variations in their pin assignment depending on the version. The ability to plug a COM Express module onto a carrier board reduces the time and cost to develop a product, as the user does not need to understand the often-complex details associated with high-speed signaling or the latest chipsets. The customer’s product lifetime is increased as newer COM Express modules can simply be plugged onto the carrier board to improve performance or lower cost as they become available. This “future proofing” is somewhat unique to COM Express.
Because target applications often need to strike a careful balance between cost and performance, a variety of COM Express form factors and board sizes are defined in the standard.
There are, of course, dozens of other small form factors that enjoy varying degrees of popularity and even more proprietary solutions offered by a single vendor to their customers. The advantage of a true open standard like COM Express is that a customer is not beholden to a single vendor. As technology evolves – and it evolves quickly – a customer can shop around for the latest technology and best prices while still maintaining backwards compatibility with previous generations of a product. This is especially appealing to those who use a COM Express board as a mezzanine “engine” controlling I/O and communications interfaces that reside on an application-specific baseboard.
All of this flexibility is not without its challenges, however. Interfaces continue to evolve, especially video interfaces, and CPU chipset manufacturers change them or update them frequently. Form factors like COM Express have limited ability to virtualize these interfaces in a way that might maintain backwards compatibility, but most of the time customers want the newest features anyway. So the COM Express family will continue to evolve, but in an orderly fashion. That is the hallmark of established standards bodies like PICMG.