CPU ID definition

During the assembly process the assembler determines the smallest instruction set containing all the instructions and gives a CPU ID value indicating the instruction set.

During the assembly process the assembler determines which instruction set (from a list of several complete instruction sets defined in the architectures or processor implementations) is the smallest instruction set containing all the instructions used in the program. The program is given a CPU ID value indicating this instruction set. Therefore a CPU ID indicates the target environment on which the object code can be run. The CPU ID value for the program is an assembler output value included in the XCOFF object file generated by the assembler.

CPU ID can have the following values:

The assembler output value CPU ID is not the same thing as the assembly mode. The assembly mode (determined by the -m flag of the as command and by use of the .machine pseudo-op in the program) determines which instructions the assembler accepts without errors or warnings. The CPU ID is an output value indicating which instructions are actually used.

In the output XCOFF file, the CPU ID is stored in the low-order byte of the n_type field in a symbol table entry with the C_FILE storage class. The following list shows the low-order byte values and corresponding CPU IDs: