CO: Addressing Modes

Question

Consider 1GHz clock frequency processor, uses different operand access modes shown below:

       

Assume that 8 cycle consumed for memory reference, 4 cycles consumed for arithmetic computation and 0 cycles consumed when the operand is in register instruction itself. What is the average operand fetch rate (in million words/sec) of the processor?

• 117.45 M words/sec
• 113.63 M words/sec
• 217.45 M words/sec
• 316.45 M words/sec

Answer 1

Total no. Of cycles= addition of followings-

{

For register 0.20*0

For immediate 0.20*0

Fo memory indirect 0.40*(8+8)=6.4

For auto indexed 0.20*(4+8)=2.4

}

Total no. Of cycles= 2.4+6.4=8.8cycles

Frequency 1ghz then cycle time=10^-9 sec

Cpu time =total no.cycles*cycletime

Cpu time=8.8x10^-9sec

Operand fetch rate(in million words per sec) =1/8.8x10^-9sec

=113.636 M words per sec

Comments

Fo memory indirect 0.40*(8+8)=6.4

For auto indexed 0.20*(4+8)=2.4

 

8+8 and 4+8 why are you adding 8 for both of them ?

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In memory inderct we need 2 memory references  [[M]]

First ref. To get effective address EA

Second ref. To access the effective address (read/wr data

Similarly for auto indexed 

1 arithmetic to calculate EA

1 mem. Ref. To access the EA (read/wr data)