Instruction	Description	Explanation
add Rd Rs Rt	Rd = Rs + Rt	Add contents of Rs and Rt register and store in register Rd
addi Rd Rs Imm	Rd = Rs + Imm	Add contents of register Rs and a constant value and store in register Rd
mul Rd Rs Rt	Rd = Rs * Rt	Multiply contents of register Rs and Rt and store in register Rd
move Rd Rs	Rd = Rs	Move the contents of register Rsinto register Rd
la Rd Addr	Rd = Addr	Load address into register Rd
li Rd Imm	Rd = Imm	Load constant value into register Rd
lw Rd Addr	Rd = word at Mem[addr]	Load a word from memory at the given address into register Rd
sw Rs Addr	Mem[addr] = Rs	Store the word from register Rs into the given address in memory
jr Rs	Jump to location in Rs	Sets the program counter to the address in Rs

See Spim Instruction Set for full set of instructions and more details