If my RTOS vendor says they provide robust partitioning, why do I need Rapita?

RTOS vendors may provide partitioning mechanisms for their multicore processors, but these do not guarantee the complete elimination of multicore interference. Instead, they are designed to provide an upper limit on interference, sometimes at the expense of average-case performance.

In aerospace, these partitioning mechanisms may be referred to as ‘robust partitioning’. AMC 20-193 (EASA's official guidance on multicore aspects of certification for ED-12C projects) and CAST-32A (the FAA’s position paper on multicore processors in avionics) identify allowances for some of the objectives if you have robust partitioning in place, but it is still necessary to verify that the partitioning is as robust as it is claimed to be.

From a certification standpoint, regardless of the methodology behind the RTOS vendor’s approach to eliminating interference, the effectiveness of the technology needs to be verified.