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User’s Manual
PPC440x5 CPU Core Preliminary
Page 56 of 589
prgmodel.fm.
September 12, 2002
2.3.4 Reserved Instruction Class
This class of instructions consists of all instruction primary opcodes (and associated extended opcodes, if
applicable) which do not belong to either the defined, allocated, or preserved instruction classes.
Reserved instructions are available for future versions of PowerPC Book-E architecture. That is, future
versions of PowerPC Book-E may define any of these instructions to perform new functions or make them
available for implementation-dependent use as allocated instructions. There are two types of reserved
instructions: reserved-illegal and reserved-nop.
Any attempt to execute a reserved-illegal instruction will cause an Illegal Instruction exception type Program
interrupt on implementations (such as the PPC440x5) that conform to the current version of PowerPC Book-
E. Reserved-illegal instructions are, therefore, available for future extensions to PowerPC Book-E that would
affect architected state. Such extensions might include new forms of integer or floating-point arithmetic
instructions, or new forms of load or store instructions that affect architected registers or the contents of
memory.
Any attempt to execute a reserved-nop instruction, on the other hand, either has no effect (that is, is treated
as a no-operation instruction), or causes an Illegal Instruction exception type Program interrupt, on imple-
mentations (such as the PPC440x5) that conform to the current version of PowerPC Book-E. Because imple-
mentations are typically expected to treat reserved-nop instructions as true no-ops, these instruction opcodes
are thus available for future extensions to PowerPC Book-E which have no effect on architected state. Such
extensions might include performance-enhancing hints, such as new forms of cache touch instructions. Soft-
ware would be able to take advantage of the functionality offered by the new instructions, and still remain
backwards-compatible with implementations of previous versions of PowerPC Book-E.
The PPC440x5 implements all of the reserved-nop instruction opcodes as true no-ops. The specific reserved-
nop opcodes are listed in Appendix A.5 on page 558
2.4 Implemented Instruction Set Summary
This section provides an overview of the various types and categories of instructions implemented within the
PPC440x5. In addition, Instruction Set on page 249 provides a complete alphabetical listing of every imple-
mented instruction, including its register transfer language (RTL) and a detailed description of its operation.
Also, Appendix A, “Instruction Summary,” lists each implemented instruction alphabetically (and by opcode)
along with a short-form description and its extended mnemonic(s).