CAST-32A, Multi-core Processors is a position paper, by the Certification Authorities Software Team (CAST). It is not official guidance, but is considered informational by certification authorities such as the

FAA The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...

and

EASA The European Union Aviation Safety Agency (EASA) is an agency of the European Union (EU) with responsibility for civil aviation safety. It carries out certification, regulation and standardisation and also performs investigation and monitori ...

. A key point is that

Multi-core processor A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such a ...

"interference can affect execution timing behavior, including worst case execution time (WCET)." The original document was published in 2014 by an "international group of certification and regulatory authority representatives." The current revision A was released in 2016. "The Federal Aviation Administration (FAA) and European Aviation Safety Agency (EASA) worked with industry to quantify a set of requirements and guidance that should be met to certify and use multi-core processors in civil aviation, described e.g. in the FAA CAST-32A Position Paper and the EASA Use of MULticore proCessORs in airborne Systems (MULCORS) research report." For applicants certifying under EASA, AMC 20-193 has now superseded CAST-32A since it AMC20-193 release on 21 January 2022. It is expected that the FAA will release its

Advisory Circular __NOTOC__ Advisory circular (AC) refers to a type of publication offered by the Federal Aviation Administration (FAA) to provide guidance for compliance with airworthiness regulations, pilot certification, operational standards, training standards, ...

AC 20-193 guidance in 2022, which is expected to be almost identical to AMC 20-193. One of the first mixed-criticality multicore avionics systems is expected to be certified sometime in 2020. The objectives of the standard are applicable to software on multicore processors, including the operating system. However, the nature of the underlying processor hardware must examined in detail to identify potential interference channels due to inter-core contention for shared resources. Verification that multicore interference channels have been mitigated can be accomplished through the use of interference generators, i.e., software tuned to create a heavy usage pattern on a shared resource. By creating stress on the shared resource, the impact of contention between cores can be measured and quantified.

Objectives

The standard presents nine objectives that must be met for Design Assurance Level (DAL) A or B. Six of the objectives apply for DAL C. The standard does not apply for DAL D or E.

References

{{Reflist RTCA standards Computer standards Avionics Safety engineering Software requirements