The basic single cycle MIPS implementation in above figure can only implement some instructions. New instructions can be added to an existing Instruction Set Architecture (ISA), but the decision whether or not to do that depends, among other things, on the cost and complexity the proposed addition introduces into the processor datapath and control. We want to add the following instruction to ISA:

Instruction: SWI Rt,Rd(Rs) NOT LWI

Interpretation: Mem[Reg[Rd]+Reg[Rs]] = Reg[Rt]

a. Which existing blocks (if any) can be used for this instruction?

b. Which new functional blocks (if any) do we need for this instruction?

c. What new signals do we need (if any) from the control unit to support this instructi