Question

2. [20%) (Textbook Chapter 5, page 275, Exercise 19 modified) Consider the following structure of the Instruction Register: Op-code Address-1Address-2 9 bits 7 bits 9 bits (a) What is the maximum number of distinct operation codes that can be recognized and executed by the processor on this machine (b) What is the maximum memory size on this machine?

Answer 1

(a) The no of bits of opcode are 7 bits. There are only 2 option for each bit : 1 and 0.

So, the maximum no of different opcode possible are

$2^7$

128

(b) Maximum size of the machines is the no of different memory instructions which can be created.

Now, no of bits in memory instruction = 7 + 9 + 9 = 25 bits

So, the no of different memory instructions possible are

$2^{25}$

So, the memory size is

$2^{25}$bytes