The basic single-cycle MIPS implementation in Figure 4.2 can only implement some

Question

The basic single-cycle MIPS implementation in Figure 4.2 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. The first three problems in this exercise refer to the new instruction:

Instruction: LWI Rt,Rd(Rs)

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

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

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

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

Explanation / Answer

Which existing blocks (if any) can be used for this instruction?
a) SEQ is a Boolean operation returning 1/true or 0/false if the two registers are equal.
reg, mux, alu
b) LWI leads the contents of a memory allocation that is the sum of two registry values.
reg, mux, alu, memory

Which new functional blocks (if any) do we need for this instruction?
a) a mux after ALU zero for Boolean 0 or 1
b) nothing

What new signals do we need (if any) from the control unit to support this instruction?
a) need control signal to operate new mux
b) nothing

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