Extending the lifecycle of PC/104

In this significant year for small form factors, the Small Form Factor Special Interest Group (SFF-SIG) thanks Paul Rosenfeld for three and a half years of leadership, during which time four specifications were developed, published, and promoted by several working groups.

As we celebrate the 20th anniversary of the PC/104 specification as a managed open standard, it is our duty to honor the contributions and efforts of its principal founder, Mr. Rick Lehrbaum. There isn’t a better way to honor him than to celebrate the sustained momentum of the PC/104 ISA bus, as well as the growth of a complementary new expansion interface: SUMIT.

PC/104 in the embedded ecosystem

Two years ago, Rick asked me whether PC/104 would survive or whether he should retire his BMW’s PC/104 vanity license plate. Immediately, I knew his concerns. For one, the PC/104 supplier community was divided over allowing the ISA bus to co-exist with PCI Express in new SBCs. However, unlike ISA, parallel PCI is expensive to add to SFF SBCs given that the parallel PCI bus is disappearing from chipsets; a PCI Express bus bridge and costly stacking connectors must be used.

Also around the time Rick was contemplating a trip to the DMV (that’s “Department of Motor Vehicles,” not a new spec), large Computer-On-Module (COM) manufacturers had already successfully converted much of the medical system OEMs from PC/104 to ETX and COM Express modules with custom carrier boards.

So much software has passed through the FDA, the FAA, and other certification agencies and organizations, and a million PC/104 systems have been deployed. Because of this, the cost of major changes is so great, and system manufacturers look for the simplest possible upgrades and technology refreshes for inevitable processor and chipset EOLs. By simply replacing the CPU module, the impact to software and certifications is, indeed, minimized.

SUMIT’s symbiosis with PC/104

When the SFF-SIG set out to define SUMIT, it did so in a manner that would least disturb the vast ecosystem and installed base of PC/104 systems. SUMIT works together seamlessly with the old 386- and 486-based CPUs that used the PC/104 bus PCI Express is a transparent upgrade to PCI for application software. USB provides simple connectivity for flash, wireless, and numerous PC-style peripherals. The LPC bus allows low-cost serial ports and other ISA-like I/O. And low-bandwidth I2C and SPI interfaces make easy work of attaching low-speed data acquisition or sensors. The SUMIT expansion interface is scalable, starting with only a single 52-pin high-density connector to keep cost and real estate at a minimum. SUMIT maps well to Intel, AMD, VIA, and DMP silicon alike, fitting perfectly into the PC/104 kingdom without replacing the ISA bus used in a million deployed systems.

As we see new proprietary interfaces, pinout definitions, and specification changes from suppliers, we can’t help but notice how stable and dependable the PC/104 (ISA) bus has been by comparison. Stability outweighs feeds and speeds in priority for many long lifecycle programs. Software compatibility is essential for OEMs, who simply want to replace their EOL CPU with little to no software impact. SUMIT provides a clean migration path that is in harmony with the PC/104 board outline and PC/104 (ISA) bus. SUMIT SBCs, such as the one shown in Figure 1 with an Intel Atom CPU and DDR3 RAM for long lifecycle applications, are now available from four manufacturers. Dozens of new PC/104 SBCs with five- to seven-year lifecycle commitments signify the viability of the bus and compatible I/O cards through the year 2020 and beyond.

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Figure 1: SUMIT SBCs like WinSystems’ PXM-C388, featuing an Intel Atom processor and DDR3 memory (pictured here), continue to succeed in the long lifecycle applications market.
(Click graphic to zoom by 1.9x)

A SUMIT-compatible alternative to the PC/104 stack is Pico-ITX at 72 mm x 100 mm, which saves more than 15 percent on board size and weight. New legacy-free designs can further take advantage of the expandability of SUMIT in the form of Pico-ITXe SBCs with Pico-I/O modules installed. More information about the SUMIT specification can be found at www.sff-sig.org.

P.S. …

To answer your question, Rick, you may proudly keep your car’s license plate. In fact, based upon the overwhelming support of board manufacturers beyond your original recruits (even in China, for example), the life span of your PC/104 license plate will likely exceed that of the BMW to which it is affixed!

Small Form Factor Special Interest Group 408-480-7900 info@sff-sig.org