2. We decide to change MARIE from an accumulator-based CPU to a general-purpose register

set CPU. Instead of the AC being used as the default register, we specify a register in the

instruction. The new instruction format is: opcode register operand. For instance,

Add R1, X means R1 = R1 + X instead of AC = AC + X. We decide to provide MARIE

with 4 registers (R0-R3). Answer the following.

a. If we want to leave the instruction length at 16 bits, what will change: the number of bits

for the op code or for the operand? And how many bits will that portion become?

b. We decide instead to lengthen the instruction to accommodate the register specifier. How

many bits long is the new instruction?

c.

With a longer instruction, we have to widen memory from 4Kx16 to 4KxY where Y is your

answer in part b. Aside from widening memory, what else needs to be widened?