Computer Organization

Question

Consider the following program segment used to execute on a hypothetical processor. Consider all the registers are of 16 bit size

I1 MOV CX,0005 ; CX ← 0005

I2 MOV BX,OFF7H ; BX ← OFF7H

I3 MOV AX,OBCAH ; AX ← OBCAH

I4 OR BX,AX ; BX ← BX (OR) AX

I5 AND DX,AX ; DX ← DX (AND) AX

I6 LOOP I3 ; LOOP till CX = 0

Processor clock frequency is 1 MHz. In which data transfer operations takes 6 cycles, data manipulation operations takes 4 cycles and transfer of control operations takes 2 cycles to execute. How much time is required to execute the program on a above CPU?

Comments

@MiNiPanda 

where we are modifying value of CX ?

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Dharmendra Lodhi

I think the decrement was implicitly taking place since they didn't mention any operation

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ok

Answer 1

92 is correct one as decrement and checking is performed simultaneously at the end.

In the iteration when the CX value is 1 which is its 5^th iteration it decrements value of CX to 0 and loop is executed until CX value is 0, so it is matched and loop will not be executed.

Hence loop executed exactly 5 times.