It is likely that every Line Replacable Unit (LRU) has a control/status processor. The prime contractor may not build anything, but just manage requirement allocation to subsystems and manage Interconnection Control Documents. Sometimes the prime contractor does not even do the integration of the final product. When there are operating systems changes it is a real nightmare to manage because it is usually not a planned event and there is no one staffed to manage all of the subcontractors. And the subcontractors are many times not funded to manage the operating system changes.
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