Overview What does Armv8.x-A mean? Why do we need the extensions? Processor implementation of Armv8.x-A Feature implementation between Armv8.x versions Armv8.x extensions and features Which extension does my processor implement? Armv8.x-A and the SBSA Check your knowledge Related information Next steps
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Processor implementation of Armv8.x-A

Each .x extension includes a set of features, some mandatory and some optional. A processor implements a .x extension if it implements all the mandatory features of that extension number, and those from all previous extensions.

For example, to be described as implementing Armv8.2-A, a processor must implement all the mandatory features from:

  • Armv8.0-A - the base specification and original release.
  • Armv8.1-A - the previous extension.
  • Armv8.2-A - the new extension.

Note: A feature might originally be optional, but later become mandatory. For example, the Dot Product instructions were optional in  all extensions from Armv8.0-A to Armv8.3-A, but became mandatory in Armv8.4-A.

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