SMALL FORM FACTOR FORUM
Too Big to Fail
Page 1 of 1
Nearly drowned out by the PC/104 buzz this month is another pioneering embedded form factor—EBX—which actually predated PC/104 by seven years and is worthy of a tribute. “Little Board,” as it was known in 1985, offered a choice of processors: Intel 186, NEC V40 and Zilog Z80.
EBX (or 5.25-inch SBC) was hatched as the “active backplane” form factor for compact computing. With dimensions close to that of a 5 ¼-inch disk drive, a system could be constructed with the minimum possible footprint. At 5.75 x 8 inch, EBX may seem large by today’s standards, but the area it occupies (L x W) barely eclipses today’s mainstream Mini-ITX form factor.
The name EBX is an acronym, as is so often the case for form factor names, for Embedded Board eXpandable. But that name wasn’t coined until 1997, when Ampro and Motorola Computer Group worked with the PC/104 Embedded Consortium to formalize the de facto standard. Naturally, the spec needed a name. Before 1988, there wasn’t even any bus expansion. The 8-bit ISA bus then appeared as a 2 x 32 row socket for an optional CGA graphics card. The full 16-bit bus brought 40 more pins—104 total—after the Consortium was formed to standardize the stacking “PC/104” ISA bus. Already, 8-bit I/O cards arrived in the market, followed by a robust ecosystem of 16-bit serial port cards, A/D cards, and eventually LAN and avionics networking. Chip-level integration had just made it possible for a minimal processor core logic circuit to fit on the tiny 3.55 x 3.775-inch form factor that was originally intended for I/O.
Why did it take five additional years for EBX to be formally announced? While expansion interfaces always have to be standardized and managed in a truly open trade group to be taken seriously, SBC form factors were simply board outlines and mounting holes, and didn’t matter much to anyone except for the enclosure designers. In 1992 as PC/104 was being standardized for I/O expansion, system OEMs were already starting to lay out large carrier boards with multiple expansion sites, mostly for I/O cards, but even sometimes for the emerging processor core modules that brought out the ISA bus to the pin-and-socket type connector pair. Thus the original computer-on-module (COM) was born, seven years ahead of DIMM-PCs and ETX modules, even though that COM acronym wasn’t created until much later.
With the EBX form factor requiring PC/104 or PC/104-Plus (PCI bus) expansion, it didn’t take long for knock-off boards with Socket 370 processor sockets for PGA processors to land from Asia, some with PC/104 family expansion and many without. Expansionless boards were known as 5.25-inch biscuit boards, named for the disk drive size that they mount conveniently over. Although low-cost boards created headaches for U.S. EBX manufacturers, they actually expanded the overall market for this size board into commercial markets. But Mini-ITX, invented by VIA with VIA processors, exploded on the scene much later and took the bottom completely out of the market. Until the first EOL notice, that is.
It’s fair to say that shipments of the much newer Mini-ITX have ramped rapidly due to the much lower prices and PC-style connector edge, adequate for plenty of commercial grade systems. Yet that does not mean that Mini-ITX should be chosen automatically regardless of the application. There are many differences in how business is conducted and how boards are designed between high-volume Asian board manufacturers and smaller on-shore EBX manufacturers.
Pity the soul who selects embedded boards on processor and price alone (refer back to the Total Cost of Ownership column). An easy life awaits the system OEM’s engineer who selects based upon all technical and business factors, much like the famed Maytag service repairman who wasn’t fighting fires because of the high product reliability. Nearly 30 years after initial shipments, the 5.75 x 8-inch EBX form factor is ironically too big to fail. Even if you don’t have the job security of working in a bailout-supported “too big to fail” corporation, your embedded system may be among the many that still use EBX or 5.25-inch SBCs. There is a healthy replacement market for such system OEMs who have enjoyed rich onboard I/O, local language support, revision control, longevity and quality. And last but certainly not least, there is the broad ecosystem of available rugged PC/104 expansion modules, many of which are still based on the ISA bus.