Section 3.3. Hardware Platforms

3.3. Hardware Platforms

The idea of a common hardware reference platform is not new. The venerable PC/104 and VMEbus are two examples of hardware platforms that have withstood the test of time in the embedded market.^[8] More recent successful platforms include CompactPCI and its derivatives.

^[8] VMEbus isn't really a hardware reference platform, per se, but based on Eurocard physical standards, the level of compatibility among multiple vendors qualifies it for the label.

3.3.1. CompactPCI

The CompactPCI (cPCI) hardware platform is based on PCI electrical standards and Eurocard physical specifications. cPCI has the following general features:

• Vertical cards of 3U or 6U heights

• Latch system for securing and ejecting cards

• Front- or rear-panel I/O connections supported

• High-density backplane connector

• Staggered power pins for hot-swap support

• Support by many vendors

• Compatibility with standard PCI chipsets

You can view highlights of and obtain specifications for the cPCI architecture at the PCI Industrial Computer Manufacturers Group (PICMG) cPCI web page, at www.picmg.org/compactpci.stm.

3.3.2. ATCA

A successor to the successful cPCI, Advanced Telecommunications Computing Architecture is the name given to the architecture and platforms designed around the PICMG 3.x series of specifications. Many top-tier hardware manufacturers are shipping or developing new ATCA-based platforms. The primary applications for ATCA platforms are carrier-class telecommunications switching and transport equipment, and high-end data-center server and storage equipment.

ATCA platforms are leading the industry trend away from in-house proprietary hardware and software platforms. Many of the largest equipment manufacturers in the telecommunications and networking markets have been slowly moving away from the custom, in-house-designed hardware platforms. This trend is also evident in the software platforms, from operating systems to so-called middleware such as high-availability and protocol stack solutions. Downsizing and time-to-market pressures are two key factors driving this trend.

ATCA is defined by several PICMG specifications. Table 3-11 summarizes these specifications.

Table 3-11. ATCA PICMG 3.x Specification Summary

Specification	Summary
PICMG 3.0	Mechanical specifications, including interconnects, power, cooling, and base system management
PICMG 3.1	Ethernet and Fiber Channel switching fabric interface
PICMG 3.2	Infiniband switching fabric interface
PICMG 3.3	StarFabric interface
PICMG 3.4	PCI Express interface
PICMG 3.5	RapidIO Interface

The platforms described in this section are the most relevant in any discussion of embedded Linux platforms today. Especially with ATCA, the industry is increasingly moving toward commercial off-the-shelf (COTS) technology. Both ATCA and Linux play increasingly important roles in this industry trend.