C-A Quantitative Approach
计算机体系结构
Chapter 3 PIPELINING Basic and Intermediate Concepts 流水线：基本概念
王奕 Estelle.ywang@gmail. com
A. 流水线基本定义
流水线的洗衣 ----开始工作越快越好
6 PM 7 8 9
Time T a s k O r d e r
10
11 Midnight
30 40 40 40 40 20
A B C D
• Pipelined laundry takes 3.5 hours for 4 loads
3-6
Why pipelining : overlapped(重叠)
连成一条流水线)
• An instruction or operation enters through one end and progresses through the stages and exit through the other end (一条指令从一流水线的一端进入从另一端出来，完成整条指令的操作) • Pipelining is an implementation technique that exploits parallelism among the instructions in a sequential instruction stream (流水线挖掘了指令流中的并行性) 3-10
3-9
What is a pipeline ?
• A pipeline is like an auto assemble line • A pipeline has many stages(流水线有多个阶段—称流水级或流水节拍) • Each stage carries out a different part of instruction or operation (每一个流水线完成指令操作的不同部分) • The stages, which cooperates at a synchronized clock, are connected to form a pipe (各个流水级在同步时钟的控制下
– implementation technique whereby different instructions are overlapped in execution at the same time.（多条指令同时重叠执行） – implementation technique to make fast CPUs
3-7
Why pipelining: more faster
• Can “launch(开始)” a new computation every 100ns in this structure • Can finish 107 computations per second
3-8
• Can launch a new computation every 20ns in pipelined structure • Can finish 5×107 computations per second
• Only deal one task each time. • This task takes “ such a long time”
ns: nanosecond 纳秒即十亿分之一秒
• Latches(锁存器), called pipeline registers break up computation into 5 stages • Deal 5 tasks at the same time.
(提高流水线性能的一些基本方法)
3-2
What is Pipelining ?
• Pipelining(流水线定义):
– “A technique designed into some computers to
increase speed by starting the execution of one instruction before completing the previous one.” ----Modern English-Chinese Dictionary
3-4
顺序执行的洗衣
6 PM 7 8 9
Time
T a s k O r d e r
10
11 Midnight
30 40 20 30 40 20 30 40 20 30 40 20 A B C D
• Sequential laundry takes 6 hours for 4 loads • If they learned pipelining, how long would laundry take? 3-5
Why pipelining : conclusion
• The key implementation technique used to Make fast CPU: decrease CPUtime.(减少CPU时间的关键技术)
• Improving of Throughput ( rather than individual execution time) (提高吞吐量，而不是单条指令的执行时间) • Improving of efficiency for resources (functional unit) (提高了资源的有限利用率)
3-3
Why Pipelining: Its Nature(流水线的本质)
• Laundry(洗衣店)
A – Ann, Brian, Cathy, Dave each have one load of clothes to wash, dry, and fold B C D
– Washer(洗衣机) takes 30 minutes – Dryer(干衣机) takes 40 minutes – “Folder”(叠衣人) takes 20 minutes
•What is pipelining?
(什么是流水线)
•How is the pipelining Implemented?
(流水线是怎么实现的)
•What makes pipelining hard to implement?
(流水线实现的困难是什么)
•Basic methods improving pipelining