The PowerPC Architecture is specified by the following documents:
System V Application Binary Interface PowerPC Processor Supplement
The PowerPC ™ Architecture: A Specification for a new family of RISC processors
Only the features of the PowerPC processor instruction set may be assumed to be present. An application must check /proc/cpuinfo to determine if any additional instruction set features are available before using those additional features. If a feature is not present, then the application may not use it.
An implementation must support the 32-bit computation mode as described in The PowerPC ™ Architecture: A Specification for a new family of RISC processors. Conforming applications shall not use instructions provided only for the 64-bit mode.
Applications conforming to this specification must provide feedback to the user if a feature that is required for correct execution of the application is not present. Applications conforming to this specification should attempt to execute in a diminished capacity if a required feature is not present.
This specification does not provide any performance guarantees of a conforming system. A system conforming to this specification may be implemented in either hardware or software.