New specification versions approved
To understand PCI-104 and where it comes from, you only have to look at the history of PC/104’s evolution. At first, there was PC/104 with a 104-pin stack-thru connector that carried the ISA bus just like the desktop computers of the day. Then, PC/104-Plus added a 120-pin connector on the opposite end of the board that carried a 33-MHz, 32-bit PCI bus in addition to the ISA bus, once again, like the desktop computers of the day. Now, PCI-104 has followed the desktop computer again by removing the ISA bus connector altogether. This new configuration frees a lot of space on a small PC/104 form factor board for systems that need only the PCI bus.
While the PCI-104 name and specification are new, the concept of a PC/104-Plus board with only the PCI bus is as old as PC/104-Plus itself. Version 1.0 of the PC/104-Plus specification envisioned just such a board but gave it the unwieldy moniker “PC/104-Plus PCI Only.” PCI-104 is the new name and it finally has its own specification.
Some people may suggest that this is the end of ISA and PC/104. Of course, these people are the same people who said ISA was dead when the consortium first released the PC/104 specification in 1992, and again when they released the PC/104-Plus specification in 1997. Here we are ready to enter 2004, and PC/104 is keeping the ISA bus alive.
Will PCI-104 replace PC/104? Nothing could be further from the truth. Many companies will continue to build PC/104 and PC/104-Plus products, and they will fill customer requirements for some time to come. Still, we need to be prepared for the future. For now it is PCI-104, but the next generation desktop PC is evolving, and the PC/104 Embedded Consortium will be ready with a stackable PC solution for this generation.
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Jim Blazer currently serves as chairman of the PC/104 Embedded Consortium and was the chairman of the technical committee that developed the PC/104-Plus specification. He is the vice chairman and chief technical officer at RTD Embedded Technologies Inc., State College, PA, and is responsible for managing a multinational engineering team designing intelligent data acquisition systems and embedded PC compatible computers. Contact Jim at firstname.lastname@example.org.