Complete custom designs are economical for large volumes or high-priced solutions, so the decision to build or buy usually isn't an either/or discussion. The plethora of different boards and module standards as well as the corresponding vendor support shows how important buying is to the embedded designer.
Many board standards also are combined with module standards. AdvancedTCA, MicroTCA, CompactPCI, VME, and VXS can take advantage of plug-in modules and mezzanine standards such as AMC (advanced mezzanine card), XMC (Express mezzanine card), and PMC (PCI mezzanine card) like Aitech's $2995 M591 PMC video adapter (Fig. 1). Air-cooled and conduction-cooled versions of the M591 are available.
On the flip side, PC/104 Plus and PCI-104 boards can be used as expansion options with standard carrier boards like EPIC, EPIC Express, and EBX. The fact that the baseboard also can be a PC/104 single-board computer mixes things up, though.
On the other hand, designers have more choices. Tradeoffs between board space, the number of connectors, heatsinks, and a host of other issues make for lively competition.
Smaller modules are having a greater impact on designs as their functionality goes up and their costs continue to go down (see "Five Tiny SBC Modules"). They're great for portable solutions, but fixed applications also can benefit from their lower cost, lower power requirements, and network support (see "Making Money With Modules,").
Standards such as COM Express bring new technologies like PCI Express and Serial ATA that tend to require more advanced board design techniques. Modules minimize this requirement while giving developers access to the latest technology. Kontron's ETXexpress-PM also addresses issues such as heat dissipation that are common on high-performance modules (Fig. 2).
Finding the right module for an application can be difficult because of the number of options and tradeoffs. But a solution probably already exists to address most problems. All you need to do is look for it.