As we predicted last September, the PC/104 Consortium is developing a PCI Express version of its popular PC/104 embedded computer module specification. “Work is already well under way” on “PC/104 Express,” according to the Consortium's July 2006 newsletter.

The need for a new PC/104-like module with a PCI Express expansion bus arose from the “EPIC Express” project. EPIC Express is equivalent to the EPIC single-board computer (SBC) form-factor, but with a self-stacking PCI Express bus replacing the PC/104-Plus standard's PCI expansion bus.

EPIC express replaces PC/104-Plus with a PCI Express equivalent
The new modules, currently called “EPIC Express I/O Expansion modules,” are the same size as PC/104 and PC/104-Plus modules, but have up to three 28-pin self-stacking serial PCI Express connectors instead of the self-stacking PC/104-Plus PCI bus. The format thus trades PCI Express for PCI, but retains the P1/P2 ISA bus. Legacy PC/104 (ISA-only) modules can coexist in a stack along with the PCI Express-enabled modules, provided the legacy modules are on top.

How PC/104 Express modules stack

Decision process

The decision of whether the Consortium should proceed with a PC/104 Express specification apparently hinges on whether it decides to adopt EPIC Express.

The original EPIC spec was announced by a five-company collaboration in March of 2004, and was adopted by the Consortium in January of 2005. It therefore seems likely that the Consortium will adopt EPIC Express as well, and thus move forward with PC/104 Express.

Additionally, if the group does adopt PC/104 Express, it will probably also create a new version of EBX that accepts the modules, most likely called “EBX Express.”

The Consortium is currently soliciting feedback from PC/104 manufacturers and users. The specification is available for download, here (PDF file).

“Please note that this proposed specification is not final and is subject to change,” the Consortium adds. “Furthermore, even if this specification is approved and/or implemented, it is entirely possible that other standards may also be proposed or implemented in the future.”

Inputs are requested by July 17, 2006 “in order for the committee to have sufficient time to review them.” Comments may be sent to the PC/104 Technical Committee via either of these two email addresses: [email protected], [email protected].

“The development of this new specification is one of the most important developments in the past 5 years in the PC/104 industry,” the PC/104 Consortium said in its newsletter.

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