what is valid PC after execution of these instruction

Question

Consider the following program segment:

Instruction Meaning        Size (words)

I1 LOAD r0, 500                  2

I2 MOV r1, r0                       1

I3 ADD ro, r1                        1

I4 INC r0                              1

I5 INC r1                               1

I6 ADD r0, r1                        1

I7 Store r1,                           2

I8 Halt Stop                           1

Assume that memory is word addressable with word size 32 bits. Program is loaded into memory location (3000)₁₀ onwards. The value of PC at the end of execution of above program is _____

Comments

Did u get ans ?

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Either it should be 3009 or 3010

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https://gateoverflow.in/35906/what-is-valid-pc-after-execution-of-these-instruction

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@arjun Sir please confirm the answer, whether it is 3009 or 3010.

Answer 1

Generally halt instructions are used for power saving purposes , so when it goes into the halt state , the processor will not fetch the next instruction as the PC will not be incremented , unless a external input comes and disturbs the halt state

 

The program will be halted if it executes the I8 instruction and the instruction is in the memory at location 3009 . So the contents of PC will be 3009 . So answer is 3009

Comments

What wil be the change if an Interrupt comes
1 Before
2 During
3 After
Execution of HALT instruction

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@Kapil SIR can u pls answer my query ?

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unless a external input comes and disturbs the halt state

It means an interrupt is necessary to CPU to read next instruction after halt instruction? 

Answer 2

The halt is implemented by pointing the program counter to the halt instruction itself so it get into a type of loop. o the HALT instruction will be at 3009 as the memeory is word addressable use word instead of bits. answer will be 3009 instead of 3010.

Comments

This is not true - nowhere in the manual is it mentioned that HALT is implemeted like this.