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Data Dependencies A dependency type that can cause a stall.

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Presentation on theme: "Data Dependencies A dependency type that can cause a stall."— Presentation transcript:

1 Data Dependencies A dependency type that can cause a stall.

2 Data Dependencies A dependency type that can cause a stall. RAW – Read After Write

3 Data Dependencies A dependency that causes a stall.

4 Data Dependencies A dependency that causes a stall. Hazard

5 Data Dependencies A technique for removing WAW and WAR dependencies

6 Data Dependencies A technique for removing WAW and WAR dependencies Register Renaming

7 Data Dependencies A software technique for reducing RAW hazards

8 Data Dependencies A software technique for reducing RAW hazards Instruction Reordering Loop Unrolling

9 Data Dependencies A hardware technique for reducing RAW hazards

10 Data Dependencies A hardware technique for reducing RAW hazards Data Forwarding Out of order execution

11 Data Dependencies The type of dependency between these two instructions: lw $1, 0($2) sw $1, 0($3)

12 Data Dependencies The type of dependency between these two instructions: lw $1, 0($2) sw $1, 0($3) RAW

13 Data Dependencies The reason WAW and WAR dependencies hurt performance

14 Data Dependencies The reason WAW and WAR dependencies hurt performance They limit instruction reordering

15 Data Dependencies Limiting factor in hardware register renaming

16 Data Dependencies Limiting factor in hardware register renaming Number of physical registers

17 Data Dependencies Limiting factor in software register renaming

18 Data Dependencies Limiting factor in hardware register renaming Number of architected registers (registers in ISA or assembly)


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