# Addressing Modes- Q12

+2 votes

A certain architecture supports an Instruction model Load Destination Source.

Load R1 A reads value at  memory location AX and it stores it in register R.
Where X is all zeroes, an offset which is appended to form complete memory address.
Assume that there are 64 cpu registers and the word size is 32 bits. Each instruction size is one word. The no of different instructions computer supports is 256. Which of the following statements is false ? This is the only type of instruction which the architecture supports to load data from memory.

What is the maximum size of memory we can refer with load instructions.

(A) $2^{32}$

(B) $2^{18}$

(C) $2^{26}$

(D) There is no theoretical limit on the size of the memory.

asked Jun 4
reshown Jun 5

## 1 Answer

+2 votes

Best answer

Since there is no way we can refer except this load instruction. we refer memory location by first appending X which is all zeroes to form a proper memory address. For eaxmple first 18 bits are 111111111111111111 then memory address formed is 11111111111111111111111100000000.
Since last 8 bits are all zeroes we can not access all memory locations and maximum memory  we can access is $2^{18}$

answered Jun 5 by (31,090 points)
edited Jun 6
```Since last 8 bits are all zeroes we can not access all memory locations and maximum memory  we can access is 2^{18}``` -> What does it meant when we say since last 8 bits are all 0's we cant access all memory locations ?
Answer: