A computer with 32bit instruct ions and 12bit addresses has

A computer with 32-bit instruct ions and 12-bit addresses has 124 2-address instructions and some number of 1-address inst ructions. How many bits are available for the opcodes of the 2-address instructions. How many 1-address instructions may be encoded? Show (in hexadecimal) how the instructions may be encoded (use the non-hexadecimal digit \'X\' to indicate the part of the instruction consumed by address(es)).

Solution

a

12 bits for 1 address.So we require 12*2 =24 bits for 2 addresses.

32-24 =8 bits are available for the opcodes of the 2 address instructions.

b.

So 2²⁰ 1 address instructions may be executed.

c

124 in decimal = 7C in hexadecimal

Opcode(20 bit)

Address(12 bit)