IITD2011

Question

What is pipelining? Whats the need? Whats the funda behind it? Does it make the processor faster?

Comments

Pipeline is basically used to increase throughput of processor(more no of instruction per sec)

Answer 1

Pipelining in simple meaning is a method of overlapping instructions with each other to achieve greater throughput. So it doesnot make processor fast but helps it to use its full potential.

FUNDA- The semester system used in colleges to increase output of engineers .. But does it increase potential of college ?? NO

Comments

yes, every year a batch passout where as B.Tech. requires 4 years.

Answer 2

Pipeline is the method by which instead of making  cpu as a single unit,its devided into various functional units with each unit carrying different tasks

for ex, in instruction pipeline (IF,ID,EX,MA,WB) ,these subtasks are called stages.

The goal of pipeline is to acheive CPI=1 ie in every cycle one instruction should get completed.This was not earlier possible because for ex an instruction takes 5 cycles to complete since cpu is single unit, you have to wait for 5 cycles for one instruction to complete..so instructions will complete at 5,10,15,20..

Now with pipeline, as soon as one instruction moves from IF to ID stage,since functional unit responsible for IF is now free ,we can fetch next instruction therefore instructions are entering at pipeline @1 instructions/cycle and leaving  @1 instructions/cycle

instructions 'll complete at 5,6,7,8,...

I'll say it'll give an illusion that processor has become faster,whereas it's the same but we are able to get more throughput(no of instructions in unit time) which is what we care about.