Electronic Design

I/O-Rich Form Factors Enable Innovation-Rich Designs

Developers can’ t get enough processing power, memory, and I/O ports. Of course, having them on-chip is just the start. Getting them connected to do useful work is another matter. Modular techniques have led to a range of form factors, from board-level systems such as VME to modules like COM Express.

The VIA Technologies Em-ITX form factor is designed to bring lots of I/O ports to the outside world with dual I/O port coast lines. The EITX-3000, the first entry for this form factor, incorporates a 1.3- GHz VIA Nano processor and the Em-IO expansion connector (Fig. 1). I/O interfaces include an 8-bit digital port, a VGA port, dual low-voltage differential signaling (LVDS) ports, dual Gigabit Ethernet, four serial ports, dual SATA II ports, six USB 2.0 ports, and HD audio. It can handle up to a 2-Gbyte DDR2 SODIMM. A Compact Flash socket is on the bottom.

The entire case is an aluminum heatsink. It supports a range of power inputs, from 7 V to 36 V dc. VIA has three expansion boards that plug into the Em-IO connector. One adds Wi-Fi support, the second adds more serial and parallel ports, and the third adds video including HDMI support. There is sufficient space inside the system for a 2.5-in. hard drive.

Em-ITX is another form factor to add to the list. It brings a lot of connectors to both sides of the system. Most motherboard form factors such as Mini-ITX and Micro ATX only have connectors on one side.

So what’s one more form factor when there are dozens to choose from? Each was designed for a purpose, such as supporting standard expansion cards either in slots like PCI and PCI Express cards for a PC or in stackable systems such as PC/104. Form factors tend to fade away as bus standards migrate to new technologies. There are no Multibus I (IEEE 796) boards around these days since single-chip micros can run rings around their 20-bit transistortransistor logic (TTL) address bus.

Yet simple interfaces die hard. The venerable ISA bus that started the PC revolution is still found in PC/104 boards. Newer incarnations such as VersaLogic’s Ocelot SUMIT-104 (Fig. 2) employ the Small Form Factor SIG SUMIT interface (see “SUMIT Brings Big Improvements In Small Packages” at www.electronicdesign. com, ED Online 18687). SUMIT is a stackable system featuring a number of interfaces, including PCI Express, LPC, USB, and SMB. The SUMIT-104 designation means the single-board computer has a SUMIT- and a PC/104-compatible ISA connector.




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