COM Express: standardized embedded modules

COM Express:
Computer-On-Module

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Figure 2
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The concept of a Computer-On-Module (COM) is not a new one within the embedded computer industry. While various COM solutions and implementations have been around for years, most never became a dominant or de facto standard. However, this changed when the PICMG COM Express specification emerged. COM Express was conceived as a COM providing a bridge from legacy interfaces such as PCI and IDE to new serial differential signaling technologies such as PCI Express, Serial ATA (SATA), USB 2.0, LVDS, and Serial DVO. This approach provides a standard COM form factor that has brought modularity and standardization to help unite embedded COM designs in the future.

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Figure 1

In late 2003, RadiSys, Intel, Kontron, and PFU Systems formed a working group to define the next-generation standard for COM modules. This working group then formalized itself within PICMG in 2004. More than 40 companies responded to the call for participation, and a PICMG subcommittee ultimately submitted a draft that resulted in today’s COM Express specification.

The COM Express specification defines two module sizes: a basic module at 95 mm x 125 mm and a pin-compatible extended module at 110 mm x 155 mm. The extended module size is intended to support both larger processors and denser memory solutions. Both sizes support internal and external graphics, multiple display devices, audio, networking, storage, and various I/O and expansion interfaces.

In addition to the usual benefits of standardization and modularity, COM architecture and methodology enable a broader level of reuse and reduced development expense, further aiding the typical time-to-market and time-to-revenue advantages. By utilizing a multiplatform architecture with COM Express, huge gains can be made through the reuse and interchangeability of modules and carriers and through common software libraries, operating system support packages, and application middleware.