Corvalent Q35SBC, User Manual, Page: 51 / 61

Appendix B PICMG1.0
The PCI Industrial Computer Manufacturers Group (PICMG) (www.picmg.org) is a consortium of
over 250 companies who collaboratively develop open specifications that adapt PCI technology for
use in high-performance telecommunications and industrial computing applications. The members of
the consortium have a long history of developing and using leading edge products for these
industries.
It was founded in 1994 with an original mission to extend the PCI standard, and currently focuses on
developing and implementing guidelines for Open Standards based computer architectures for
telecommunications, industrial, and military use.
The PCI-ISA Passive Backplane Standard was developed by PICMG member companies to adapt
desktop PCI standards for industrial applications.
Desktop computers generally have most of their circuitry on a single large "motherboard" that
mounts to the bottom of the computer's chassis. While this is the least expensive packaging method,
it leaves a lot to be desired when used in industrial applications. The motherboard, usually
constructed from 0.062" material, is thin enough and large enough to flex when inserting plug-in
boards. This flexure can, and often does, break small traces and solder joints on fine pitch surface
mount devices. Replacing a motherboard requires complete disassembly, removing all cards and
cables from the system. Downtime ranges from 30 minutes to several hours. This is unacceptable for
many critical industrial or telephony applications.
The PCI-ISA passive backplane standard moves all of the components normally located on the
motherboard to a single plug-in card. Looking much like a standard ISA or PCI card, a PCI-ISA CPU
card has two edge connectors on it - one for the PCI bus and one for the ISA bus. The
"motherboard" is replaced with a simple "passive backplane" that has only connectors soldered to it.
This backplane is simple and robust, with a very low likelihood of failure.
Passive backplane systems have several advantages. First, they are more maintainable than a
motherboard system and have a much lower mean time to repair (MTTR). Second, it is easy to
upgrade to a newer and faster processor if desired. Third, passive backplane CPU's are generally
manufactured by industrial suppliers who provide configuration control and longer product lifetimes
than those typical of the desktop world.
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