Appendix B
B-2 MIPS R4000 Microprocessor User's Manual
B.1 Instruction Formats
There are three basic instruction format types:
• I-Type, or Immediate instructions, which include load and
store operations
• M-Type, or Move instructions
• R-Type, or Register instructions, which include the two-
and three-register floating-point operations.
The instruction description subsections that follow show how these three
basic instruction formats are used by:
• Load and store instructions
• Move instructions
• Floating-Point computational instructions
• Floating-Point branch instructions
Floating-point instructions are mapped onto the MIPS coprocessor
instructions, defining coprocessor unit number one (CP1) as the floating-
point unit.
Each operation is valid only for certain formats. Implementations may
support some of these formats and operations through emulation, but
they only need to support combinations that are valid (marked V in Table
B-1). Combinations marked R in Table B-1 are not currently specified by
this architecture, and cause an unimplemented operation trap. They will
be available for future extensions to the architecture.
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