MIPS R4400 用户手册，指令集介绍-The R4000 processor provides complete application software

compatibility with the MIPS R2000, R3000, and R6000 processors.

Although the MIPS processor architecture has evolved in response to a

compromise between software and hardware resources in the computer

system, the R4000 processor implements the MIPS ISA for user-mode

programs. This guarantees that user programs conforming to the ISA

execute on any MIPS hardware implementation.