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Many military system designers select PC/104 because its ultra-small, 3.55-in. x 3.775-in. form factor enables an off-the-shelf solution for applications that may previously have been possible only with a custom CPU design. For example, the small size allows PC/104 CPUs, and even complete multi-board systems, to be placed in the nose cone of a missile (Figure 1), or fit nicely inside a small UAV.
By leveraging the PC as its core foundation, PC/104–and its wider community of form factors including PC/104-Plus, PCI-104 and EPIC–has been able to leverage all facets of the PC infrastructure. Last year the PC/104 Embedded Consortium brought PCI Express into the realm of PC/104. The Consortium has detailed a consolidated and consistent stackable PCI Express roadmap, starting with the adoption of the PCI/104-Express and PCIe/104 specifications. The spec brought PCI and PCI Express buses together to form PCI/104-Express. For additional room on a module, the PCIe/104 removes the PCI bus. This new stackable PCI Express bus can be immediately incorporated across the Consortium’s 104, EPIC and EBX form factors. A new high-speed surface mount connector was specially sponsored and designed for this application.
Maximum effort went into configuring this connector so that it was capable of handling the rugged environments of the embedded market, optimized for the 0.600-inch (15.24 mm) stack height of the PC/104 architecture, and capable of transporting the high-speed signaling of PCI Express over large stack heights while keeping PCI Express Gen 2 in sight.
Maintaining the strategy of preserving ties to legacy PC/104, the PC/104 Embedded Consortium’s major ESC announcement this year was the addition of USB connections to the stackable PCI/104-Express and PCIe/104 specifications. Since the adoption of those two specs a year ago, a number of vendors have rolled out products based on the PCI/104-Express and PCIe/104 specs. The PCI Express links can be configured as multiple x4 links or x8 links. The addition of the industry-standard USB will help provide quick connectivity for add-on modules that have USB-driven devices.
Some expect that this marrying of USB and PCI Express to the PC/104 world may eventually be the elimination of PCI bus for the PC/104 realm, even though the venerable ISA bus will still have a place. Any application–whether it’s in the embedded or desktop/server space–that needs performance will want to migrate to PCI Express or USB anyway. In contrast, ISA still has a role as a low-speed, easy-to-implement interface to sensors, analog/digital I/O and so on.
The roundup on the following pages showcases some representative examples of PC/104, PC/104-Plus, PCI/104-Express and EPIC single board computer products. Many of these vendors offer both PC/104 and EPIC families of products. For the purposes of this product roundup, each vendor was asked to include just one of their latest and greatest products.