The instruction format of a computer is given by one indirect bit, opcode bits,

Question

The instruction format of a computer is given by one indirect bit, opcode bits, register address bits, immediate operand bits and memory address bits. It occupies one memory word of 64 bits.

1. The instruction format of a computer is given by one indirect bit, opcode bits, register address bits, immediate operand bits and memory address bits. It occupies one memory word of 64 bits. a- How many memory addresses can be generated if the memory size is 1 Giga Bytes (Giga-230)? Number of address bits Number of addresses b-Complete the missing fields in the following instruction format, given that the number of opcodes is 128, the immediate operand field occupies 24 bits and the instruction occupies one memory word. · Opcode Register address immediate operand Memory addr c- If the immediate value is increased by combining it with the address field in the above instruction. Find the largest positive and smallest negative immediate values that can be stored on the addres:s field, before and after combining it with the address field. Range before combining (-+) Range after combining(t)

Explanation / Answer

a.

memory size = 1 Giga Bytes = 230

b.

2 bits

Bits for register = 64 -(1+7 +24 + 30) = 64 - 62 = 2 bits

c.

after combining immediate value and address field,immediate value size = 224 + 230 = 254

24/2 = 12

54/2 = 27

range is obtained by dividing the bits by 2 on both sides of 0 and postive number is one short to accomodate 0

Number of address bits Number of addresses 30 230 = 1073741824

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