PC/104 Expands to Meet New Needs

This 17-year-old, small-form-factor, workhorse design platform continues to grow by incorporating PCI Express and accommodating lower-power CPUs.

In just the last year, the PC/104 family of small-form-factor, stackable board standards has undergone several changes. Analysts who follow this embedded-market niche now include several specifications under the PC/104 umbrella beyond PC/104 and PC/104-Plus. Although designers’ needs remain fairly stable, emerging high-end applications require the higher speeds that are possible with PCI Express as well as lower power.

PC/104 is more than a form factor. “It’s also a stacking technology incorporating industry-standard buses and a configuration with specific mounting holes in unique locations,” says Paul Haris, president of the PC/104 Consortium. Because the design platform’s technology follows the mainstream desktop-PC market, PC/104 leverages the entire PC industry’s variety and volume of chips and software. As a result, designers can independently build systems using central-processing- unit (CPU) and I/O cards that work together.

Figure 1: PC/104 Family CPU Module Shipments Segmented by Vertical Market, 2008 (% of Dollar Volume Shipments); 2008 Total: US$ 161.9 Million

Aside from its small, 90-x-96-mm module outline, PC/104’s main attraction is the ruggedization provided by the way that the boards stack and screw together. This explains its popularity in industrial automation/control and military/aerospace applications. With their stringent environmental and thermal requirements, they are its biggest users (see Figure 1). Because these systems have long product lifecycles, they retain older technologies like the ISA bus. “The original PC/104 ISA bus applies to the many lower-speed applications across the entire embedded market from commercialgrade to mil-spec,” explains Haris. Those uses also include medical systems and the type of point-of-sale/kiosk applications that are more common in Europe and Asia than the U.S., emphasizes Steve Berry, president of Electronic Trend Publications.

Even where some application requirements have pushed designers to use faster, more powerful processors, they still need the lower-speed ISA interconnects. Such interconnects allow them to support legacy requirements in the installed base, such as simple background monitoring of systems, explains Tom Barnum, vice president of strategic accounts for VersaLogic. “On our platforms moving forward, we’re supporting PCI Express for higher throughput requirements, but retaining the ISA connectors.”

Figure 2: WinSystems’ new PPM-LX800-G PC/104-Plus SBC is based on the 0.9-watt AMD LX 800 CPU.

The Need For Lower Power

According to Berry, the industry-wide push for lower power consumption is most visible in smaller form factors like PC/104, where it becomes more difficult to get the heat out. Although new processors from Intel, VIA, and AMD provide more processing power, they require less electrical power to operate. These CPUs, such as the Intel® Atom™ processor and the VIA Nano, are easier to cool. Yet the multiple on-board power supplies required present challenges, says Bob Burckle, vice president of WinSystems. On the plus side, Burckle points out that Intel is guaranteeing seven years for its Intel Atom processors and AMD has said its LX800 will be available through 2015, guaranteeing availability for longer-lifecycle PC/104-based embedded systems. For example, WinSystems’ new PPMLX800- G PC/104-Plus SBC is based on the 0.9-W AMD LX 800 CPU (see Figure 2).

Kontron has no plans at present to build another new single-board computer (SBC) in the PC/104 form factor. Yet according to Christine Van De Graaf, product marketing manager for the embedded modules division, “We must remain compatible with it. We see that PC/104 needs lower-power CPUs, such as the AMD LX800 and the Intel Atom processor N270.” PC/104 is still the best fit for a CPU board in applications that must go into a small space—ones that either don’t need a lot of customization or have space for stacking up boards if customization is needed. It also is the optimal choice for applications that only require off-the-shelf I/O rather than advanced capabilities like Gigabit Ethernet.

Emerging High-End Applications

As the PC/104 design platform continues to incorporate industry- standard desktop PC buses, such as PCI and PCI Express, the PC/104 Consortium has issued five specifications. The original PC/104 specification uses the ISA bus while PC/104-Plus adds PCI. PCI-104 removes ISA and keeps PCI for more room on the module.

Figure 1: PC/104 Family CPU Module Shipments Segmented by Vertical Market, 2008 (% of Dollar Volume Shipments); 2008 Total: US$ 161.9 Million

About a year ago, the consortium introduced two more specifications: PCI/104-Express, which combines PCI and PCI Express, and PCIe/104, which retains only PCI Express. Around the same time, the Small Form-Factor Special Interest Group (SFF-SIG) standards organization debuted and released a new PCI Express specification based on the same-size module outline, but using a different stackable architecture called Stackable Unified Module Interconnect Technology (SUMIT). The SIG’s new stackable PCI Express specification, originally called Express104, is now named SUMIT-ISM (Industry Standard Module).

Because product shipments are still low, analysts like Venture Development Corp.’s Heikkila are tracking the new PCI Express architectures from both organizations in a single category. Heikkila dubs this combined category “PC/104 Express” (see Figure 3). PCI Express will play in an emerging higher end of PC/104-based small, mobile, high-performance systems that will benefit from its rugged characteristics, he predicts. “This high end is moving slowly. But in five to ten years, it will experience higher volumes.”

The bread and butter of PC/104 board makers are mainstream embedded applications that need rugged, reliable, efficient products. “No one in the embedded space is rushing to buy faster CPU technologies just for the sake of having the fastest CPU,” states Doug Stead, president of Tri-M Systems. “Truly embedded products do one or two tasks for the product’s life expectancy. Embedded engineers don’t want extra cost in their BOM (bill of materials) just to have a 3-GHz quad-core processor when a 900-MHz single-core CPU is overkill.” In the embedded space, the only need for bus speeds faster than 16/32-bit PCI is for sending video data—not process-control data.

At the same time, PC/104’s future may lie increasingly in I/O expansion—even when the SBC itself is not PC/104-based, says Kontron’s Van De Graaf. “We see PC/104 being used more for expansion boards in the future—not just for SBCs.” Adlink’s Colin McCracken, director of technical marketing, states that the value of the larger small-form-factor-board ecosystem reinforces the usage of PC/104 interfaces across different-sized boards. “You can use PC/104 I/O cards on top of EPIC, EBX, and even non-standard SBCs—not just PC/104 SBCs,” he emphasizes. “The larger the SBC, the more integrated I/O there will be on that board, so fewer add-on cards are needed. On an EPIC or EBX motherboard, for example, you’d have a very short but broad-based system. On a PC/104 SBC, you’d have a taller system because the I/O card stack will be higher.”

Ann R. Thryft has over 20 years of industry knowledge in embedded hardware and software. An award-winning trade journalist, she has held editorial positions with EDN, EE Times, Nikkei Electronics Asia, RTC Magazine, COTS Journal, Computer Design, and Electronic Buyers’ News. She provided the analyst commentary for Evans Data Corp.’s Embedded Systems Development 2007 strategic report. Thryft can be reached at athryft@earthlink.net.