forwarding' and one further example of a 'read$-$after$-$write' hazard that

$6$

results in an interlock. Identify all three.

Mnemonic

MOV r $1,$#$00004A000$

MOV $22,$ #$0$x$00003$BC$0$

MOV r$0,$ r$1,$ LSL #$4$

SUB $r3,r2,r1$

ADDr$4,r1,r2$

$RSBr5,r4,r0$

MOV $r6,$ #$0$x$000002$E $4$

MOV $r7,$#$00002E400$

ADDr$2,r1,r0$

Comment

; move $0$x$0004$A$000$ into r$1$

; move $0$x$00003$BC$0$ into r$2$

; left shift $r1$ by $4$ bits

; subtract $r1$ from $r2$

; add $r1$ and $r2,$ sum in $r4$

; subtract $r4$ from r$0$

; move $0$x$000002$E$4$ into r$6$

; move $0$x$0002$E$400$ into $r7$

; add $r1$ and $r0,$ sum in $r2$

c$)$ i$)$ Draw a pipeline diagram for the program given above in part b$),$

$5$

assuming that it is executed using the ARM$9$ microprocessor.

ii$)$ What is the performance, as measured in 'clocks per instruction'

$2$

$($CPI$)?($counting clock cycles from the execute stage of the first instruction to the execute stage of the last instruction$)$

$4$

iii$)$ How can the instructions be reordered so that 'read$-$after$-$write' hazard do not occur without changing the function of the programme?

Total

$25$