In one of the latest consortia-related activities, the Small Form Factor Special Interest Group (SFF-SIG) and its membership are introducing an interconnect technology specifically tailored to Computer-On-Modules (COMs). Here's a first look at this new specification.
With the advent of the low-power, high-integration Intel Atom and VIA Nano x86 processors and chipsets, the special manufacturing issues associated with some of their high-ball-count micro BGAs, and the newer high-speed serial interfaces, standard SBC and custom board designers now face a "sizable" problem. Engineers struggle with knowing how to design, debug, and manufacture using this technology in a timely and cost-effective manner while reacting quickly to market and customer needs.
At the 2009 Embedded Systems Conference in Silicon Valley, the SFF-SIG is introducing a specification that will address these issues. Computer-On-Module Interconnect Technology (COMIT) is targeted at SFF processor modules and baseboards that leverage the latest ultra-mobile and moderate-power processor/chipset combinations.
The embedded industry needs a standard COM specification that utilizes modern connector technology and manufacturing practices to focus on both current and future processors and their high-performance I/O interfaces. COMIT fulfills this need by defining a tiny processor module that fits within the footprint of industry-standard embedded system form factor boards such as EBX, ECX, EPIC, and PC/104, as well as any other standard or custom-designed boards.
Existing industry standards for board-level computer technology typically describe a mechanical board form factor including the board-to-board electrical interconnect. This ties all future board designs based on the standard to the I/O available at the time of the specification's conception and often leaves no path forward for future chipsets and interface features.
COMIT breaks with this past practice by separating form factor standards from board interconnect standards. The COMIT high-speed connector system supports the most common serial I/O and legacy interfaces available in today's low-power chipsets; it is also completely independent of module size or implementation.
Defining the connector
COMIT uses the SEARAY high-speed, high-pin-density, rugged, low-cost connector system from Samtec. This second-sourced, compact connector is well-suited for both commercial and industrial applications in current and future embedded systems designs. SEARAY is capable of handling differential signaling rates of 9 GHz bandwidth, which can support interfaces like PCI Express Gen 2 and USB 3.0.
In a single 240-pin high-speed connector, COMIT supports three x1 PCI Express lanes; one x4 PCI Express lane; six USB 2.0 channels; VGA, SDVO, and dual 18/24-bit LVDS video interfaces; HD Audio; two SATA channels; Gigabit Ethernet; 8-bit SDIO; Tx/Rx serial channel; LPC bus; SPI/Microwire; SMBus/I2C bus; system clock; and control signaling plus ample power and ground (see Figure 1). COMIT's connector pin assignments are optimized for signal integrity, relative layout ease, and optimal routing.
Figure 1 | COMIT supports the most common serial I/O and legacy interfaces available in today's low-power chipsets.
I/O for the future
Besides signals and a connector, COMIT architects considered the technology required at the board design, manufacturing, and assembly levels for the latest high-pin-count CPUs and chipsets. Pin densities on these devices have increased to more than 800 pins per square inch. As chip miniaturization continues on the downward path toward tighter integration and smaller packaging, manufacturing processes must keep up.
COMIT delineates a technological line between the processor and its corresponding application-oriented baseboard host. A COMIT module built with high-density interconnection technology can be plugged into a less complex, application-specific I/O board optimized to the system enclosure and real-world cabling issues. System designers can thus upgrade to the latest-generation processors on their baseboards, allowing easy migration to future processors for performance/feature enhancement while mitigating cost, time to market, and obsolescence for either the processor or the baseboard.
An engineer's decision of which COM module to use is based on size, technology, and cost. Board, box, and system-level designers are under constant pressure to make products smaller. COMIT simplifies difficult and complex design and manufacturing issues by separating the CPU and I/O boards. The net result is a fast, low-power, high-integration processor module that can be used on a variety of baseboards geared to cost, size, and application-specific I/O requirements. ➤
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