PCI-104: The standard evolves

For more than a decade, the PC/104 Consortium has been developing a road map for the evolution of the PC/104 form factor. These custodians added the next variation on the PC/104 and PC/104-Plus specifications when they developed the PCI-104 specification. PCI-104 is indistinguishable from the PC/104-Plus form factor with one exception. The newest variation of the PC/104 specification leaves out the space consuming ISA bus connector.

The PCI-104 specification, with the size and rugged characteristics of its predecessors, provides processor independence. Not limited to the x86 architecture, PCI-104 is compatible with XScale, PowerPC, ARM, Pentium, and other processors.

According to Advantech, a leading global PCI-104 manufacturer, “With the introduction of PCI-104, a PCI only version of PC/104-Plus without an ISA bus on board, a new standard is available that supports more intensive computing applications on the same small form factor with the same robust qualities PC/104 is famous for. This makes it easier for developers to replace larger form factor boards with the same or greater computing capability, using a more compact and robust PCI-104 CPU module.”

The cards are designed to be stacked without a backplane. PCI-104 cards may be included in the stack with both PC/104 and PC/104-Plus cards. The stack configuration requires the PC/104 modules to be at the top of the stack, as they do not include the PCI bus. If PC/104-Plus cards are used, they must be stacked below the PCI-104 cards.

Adding other modules to expand the capabilities of the CPU using stack-through connectors has two benefits. Namely, reducing the system size and ruggedizing it to better withstand shock and vibration.

One example of a high performance PCI-104 CPU module is the new Intel Pentium M 1.1 GHz CPU from Advantech. The PCM-3380, shown in Figure 1, supports the most demanding embedded applications. With dual display support, the new PCI-104 module is suitable for graphic intensive medical applications as well as multimedia applications requiring superior graphics support and processing power. The PCI-104 expansion connector opens this board up to a world of expansion possibilities, adding increased capabilities. An optional version of the PCM-3380 is available with a 1.6 Ghz processor.

The PCI-104 specification defines the PCI bus connector as a “4 x 30 (120-pin) 2mm pitch stack-through connector as opposed to the 124-pin edge connector on the standard 32-bit PCI Local bus. The 120-pin PCI does not support 64-bit extensions, JTAG, PRSNT, or CLKRUN signals.”

The PCI-104 specification document is available at www.pc104.org/technology/pc104_tech.html. More information on PCI is available on the PCI SIG website, www.pcisig.com.

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For further information, contact Rosemary at rkristoff@opensystems-publishing.com.