236 views
In base index addressing mode how many number of cycles for operand fetch is to be required?

is it 8 ?

Assume

4cycles =consumed for memory reference

2 cycle = consumed for arithmetic operations

1cycle =consumed when operand present in register

0 cycle = consumed when operand present in instruction itself

Indexed

Add R3, (R1 + R2)

R3 <- R3 + M[R1+R2]

Useful in array addressing:
R1 - base of array
R2 - index amount
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+1
R3<- R3+ M[R1+R2]

for fetching data from R1 and R2 we need 1+1= 2 cycles .

Now we have to add the value of R1 and R2 (which will give us the memory location where the operand is present) which will take 2 cycles( arithmatic operation).

Now we have to fetch the operand from memory which will take 4 cycles.

Now we have one operand and we need the second operand for addition operation i.e. R3

fetching R3 will take 1 cycle.

so total cycles=2+2+4+1=9 cycles.
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I think you forgot to count 2 cycles to sum with R3.
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we need to count the cycles for operand fetch only. We have both operands available for addition now so the instruction can execute further.
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oh yes! I didn't see the question carefully.
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@Manu Thakur @Gaurav Joshi how 4 cycle for operand fetch after the effective add. calculation?? Can you please help to understand this?

Now we have to fetch the operand from memory which will take 4 cycles.Ca