Cavaet Emptor: I just cracked open a so-called' industrial PC. They charged premium price for a simple NEMA-4 enclosure, holding a 486 ??
IMHO: An industrial PC should have:
redundant power supplies front-accessible components, i.e., should be able to access everything from the front. MTTR of any component within 5 minutes MTBF of all components of 100,000 hours
Extras: tolerate vibration from equipment higher temperature range
I have used commercial PC on an incinerator monitoring application for city of detroit. We vacuumed inside every 30-days.
Some of the industrial computers, are very difficult to service (compared to HP, DELL, etc).
I agree with Bill here, if you look at them with a jaded eye, many of the differences simply make them less generic (read single sourced and more expensive) rather than more robust. The passive backplane models actually stand to be less reliable because the majority of problems are with connections and they have more of them. Temperature specs may be better, but off-the-shelf motherboards sell in the hundreds of thousands and are very well characterized and reliable. The IPC's sell in the hundreds at best and are typically done by small specialist operations with limited resources. I have elected to try to get the best of both worlds. A high volume, proven reliable commodity motherboard in an industrial case with the things that do matter like spec'ed power supply, engineered cooling and shock & vibration isolation for the drives (if any). I try to make a volume buy of a MB we have used for at least a year (we currently use FIC VA-503+ Socket 7 MBs ) definately not bleeding edge. I have 5 of these locally that will run RedHat 6.0 for 6 months without interruption between service intervals and several more out in the world that may have never been serviced. The least reliable components are the fans, we check them really close and replace them with better fans at the first hint of a problem.