Question

consider adding a new instruction, swap rd, rn , to our architecture, which will swap the data stored in rd and rn . discuss the necessary changes that must be made to the datapath above. there is no need to design a new datapath - just discuss what should be added to the existing one.

Answer 1

To add the 'swap rd, rn' instruction to the existing architecture, a new multiplexer needs to be introduced in the datapath to select between the original and swapped values from the registers. The control signal of this multiplexer would depend on the opcode of the instruction being executed.

Step-by-step explanation:

Adding a new instruction, swap rd, rn, to the existing architecture requires certain changes to the datapath. The primary change would involve introducing a new multiplexer to select the source of the data to be transferred. This multiplexer would choose between the original source values from registers rd and rn, and the swapped values from these registers.

To implement this swap instruction, the datapath needs to be modified as follows:

1. Add a new multiplexer after the registers rd and rn.
2. The control signal of this multiplexer would depend on the opcode of the instruction being executed.
3. If the opcode is for the swap instruction, the control signal for the multiplexer would be set to select the swapped values from rd and rn.
4. Otherwise, the control signal would be set to select the original values from rd and rn.