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.
TOO MANY FORM FACTORS 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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