| Multi-core Processors | |
| Year Started: | 2014 |
| Version: | A |
| Organization: | FAA |
| Abbreviation: | CAST-32A |
| Domain: | Aviation |
| Website: | faa.gov |
CAST-32A, Multi-core Processors is a position paper,[1] by the Certification Authorities Software Team (CAST). It is not official guidance, but is considered informational by certification authorities such as the FAA and EASA. A key point is that Multi-core processor "interference can affect execution timing behavior, including worst case execution time (WCET)."[2]
The original document was published in 2014 by an "international group of certification and regulatory authority representatives."[3] 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proCessORs in airborne Systems (MULCORS) research report."[4] For applicants certifying under EASA, AMC 20-193 has now superseded CAST-32A since its release on 21 January 2022. It is expected that the FAA will release its Advisory Circular AC 20-193 guidance in 2023, which is expected to be almost identical to AMC 20-193.[5] [6]
One of the first mixed-criticality multicore avionics systems is expected to be certified sometime in 2020.[7] The objectives of the standard are applicable to software on multicore processors, including the operating system.[8] [9] However, the nature of the underlying processor hardware must be examined in detail to identify potential interference channels due to inter-core contention for shared resources.[10] 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.[11]
The paper presents ten objectives that must be met for Design Assurance Level (DAL) A or B. Six of the objectives apply for DAL C. The paper does not apply for DAL D or E.
| Objective | Applicable Design Assurance Levels | |
|---|---|---|
| MCP Planning 1 | A, B, C | |
| MCP Resource Usage 1 | A, B, C | |
| MCP Resource Usage 2 | A, B | |
| MCP Planning 2 | A, B, C | |
| MCP Resource Usage 3 | A, B | |
| MCP Resource Usage 4 | A, B | |
| MCP Software 1 | A, B, C | |
| MCP Software 2 | A, B, C | |
| MCP Error Handling 1 | A, B | |
| MCP Accomplishment Summary 1 | A, B, C |