PICMG 1.0 CPU Cards look much like standard ISA cards with extra gold finger connections for the ISA bus and the root PCI bus.
The "motherboard" is replaced with a simple "passive backplane" that has only PCI and ISA connectors attached to it.
These backplane connections include a dedicated system slot of the PICMG 1.0 CPU and various connections for standard ISA and PCI peripheral cards.
This backplane is simple and robust, with a very low likelihood of failure, given its passive nature.
This allows a much lower Mean Time to Repair than classic computer motherboard approaches, as electronics associated with CPUs can be replaced without having to remove peripheral devices.