1. Data Hazard Example
(stall)

2. Code add $1, $1, $1 lw $2, 0($1) add $4, $2, $5 add $4, $4, $2
Where
contents of $1 is initially 6
contents of $2 is initially 20
contents of $4 is initially 32
contests of $5 is 57
contents of memory location 12 is -1

3. add $1, $1, $1

4. lw $2, 0($1)
add $1, $1, $1 1 6 1 6 1 1 1 1

5. add $4, $2, $5
lw $2, 0($1)
add $1, $1, $1 1 6 6 6 2 12 ? 6 6 1 2 2 1 1 1

6. Hazard Unit compares these registers
add $4, $4, $2
add $4, $2, $5
lw $2, 0($1)
add $1, $1, $1 1 2 5 2 1 2 20 6 12 5 12 10 12 57 2 12 5 4 2 2 1 5 1 1 1 2

7. add $4, $4, $2 add $4, $2, $5 nop lw $2, 0($1) add $1, $1, $1 2 20 512 -1 1 57 12 12 2 12 5 5 2 4

8. add $9, $4, $4 add $4, $4, $2 add $4, $2, $5 nop lw $2, 0($1) 4 32 20-1 -1 2 -1 2 01 56 -1
20 -1 57 -1 57 12 4 12 2 2 5 4 4 4 2 2 5 1

9. add $9, $4, $4 add $4, $4, $2 add $4, $2, $5 nop 4 32 32 56 4 56 10 55-1 -1 4 56 4 4 2 4 4 9 4 4 4 1 2

10. add $9, $4, $4
add $4, $4, $2
add $4,
$2, $5 32 56 55 55 10 4
110 56 32 56 56 55 56 55 10 55 4 9 4 9 4 4 1 4 4 1

11. add $9, $4, $4
add $4,
$4, $2 4 55 55 55
110 9