# 程序代写代做代考 Exercise 4.13

Exercise 4.13
In this exercise, we examine how data dependencies affect execution in the basic 5-stage pipeline

described in Section 4.5. Problems in this exercise refer to the following sequence of instructions:

Instruction Sequence

a. SW R16, -100(R6)
LW R4, 8(R16)

b. OR R1, R2, R3
OR R2, R1, R4
OR R1, R1, R2

Without Forwarding With Full Forwarding With ALU-ALU Forwarding Only

a. 250 ps 300 ps 290 ps

b. 180 ps 240 ps 210 ps

4.13.4 [10] <4.5> What is the total execution time of this instruction sequence without forwarding and

with full forwarding? What is the speedup achieved by adding full forwarding to a pipeline that had no

forwarding?

4.13.5 [10] <4.5> Add NOP instructions to this code to eliminate hazards if there is ALU-ALU forwarding

only (no forwarding from the MEM to the EX stage).

4.13.6 [10] <4.5> What is the total execution time of this instruction sequence with only ALU-ALU

forwarding? What is the speedup over a no-forwarding pipeline?

Exercise 4.13
In this exercise, we examine how data dependencies affect execution in the basic 5-stage pipeline

described in Section 4.5. Problems in this exercise refer to the following sequence of instructions:

Instruction Sequence

a. SW R16, -100(R6)
LW R4, 8(R16)

b. OR R1, R2, R3
OR R2, R1, R4
OR R1, R1, R2

Without Forwarding With Full Forwarding With ALU-ALU Forwarding Only

a. 250 ps 300 ps 290 ps

b. 180 ps 240 ps 210 ps

4.13.4 [10] <4.5> What is the total execution time of this instruction sequence without forwarding and

with full forwarding? What is the speedup achieved by adding full forwarding to a pipeline that had no

forwarding?

a.

a. No forwarding: 5 × 250ps = 1250ps; full-forwarding: 4 × 300ps = 1200ps;
1250ps

1200ps
=

1.04 𝑡𝑖𝑚𝑒𝑠 𝑓𝑎𝑠𝑡𝑒𝑟

b. No forwarding: 7 × 250ps = 1750ps; full-forwarding: 3 × 300ps = 900ps;
1750ps

900ps
=

1.94 𝑡𝑖𝑚𝑒𝑠 𝑓𝑎𝑠𝑡𝑒𝑟

b.

a. No forwarding: 5 × 180ps = 900ps; full-forwarding: 4 × 240ps = 960ps;
900ps

960ps
=

.94 𝑡𝑖𝑚𝑒𝑠 𝑎𝑠 𝑓𝑎𝑠𝑡

b. No forwarding: 7 × 180ps = 1260ps; full-forwarding: 3 × 240ps = 720ps;
1260ps

720ps
=

1.75 𝑡𝑖𝑚𝑒𝑠 𝑓𝑎𝑠𝑡𝑒𝑟

4.13.5 [10] <4.5> Add NOP instructions to this code to eliminate hazards if there is ALU-ALU forwarding

only (no forwarding from the MEM to the EX stage).

a. SW, LW, NOP, NOP, ADD

b. OR, OR, OR

4.13.6 [10] <4.5> What is the total execution time of this instruction sequence with only ALU-ALU

forwarding? What is the speedup over a no-forwarding pipeline?

a.

a. 5 × 290ps = 1450ps;
1250ps

1450ps
= 0.86 𝑡𝑖𝑚𝑒𝑠 𝑎𝑠 𝑓𝑎𝑠𝑡

b. 3 × 290ps = 870ps;
1750ps

870ps
= 2.01 𝑡𝑖𝑚𝑒𝑠 𝑓𝑎𝑠𝑡𝑒𝑟

b.

a. 5 × 210ps = 1050ps;
900ps

1050ps
= 0.86 𝑡𝑖𝑚𝑒𝑠 𝑎𝑠 𝑓𝑎𝑠𝑡

b. 3 × 210ps = 630ps;
1260ps

630ps
= 2 𝑡𝑖𝑚𝑒𝑠 𝑓𝑎𝑠𝑡𝑒𝑟

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