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.