In this exercise,we examine how pipelining affects the clock cycle time of the p
ID: 3863024 • Letter: I
Question
In this exercise,we examine how pipelining affects the clock cycle time of the processor. Problems in this exercise assume that individual stages of the datapath have the following latencies:
IF
ID
EX
MEM
WB
250 ps
350 ps
150 ps
300 ps
200 ps
Also, assume that instructions executed by the processor are broken down as follows:
ALU/Logic
Jump/Branch
LDUR
STUR
45%
20%
20%
15%
4.16.1 [5] <§4.5> What is the clock cycle time in a pipelined and non-pipelined processor?
4.16.2 [10]<§4.5>WhatisthetotallatencyofanLDURinstructioninapipelined and non-pipelined processor?
4.16.3 [10] <§4.5> If we can split one stage of the pipelined datapath into two new stages, each with half the latency of the original stage, which stage would you split and what is the new clock cycle time of the processor?
4.16.4 [10]<§4.5>Assumingtherearenostallsorhazards,whatistheutilization of the data memory?
4.16.5 [10]<§4.5>Assumingtherearenostallsorhazards,whatistheutilization
of the write-register port of the “Registers” unit?
IF
ID
EX
MEM
WB
250 ps
350 ps
150 ps
300 ps
200 ps
Explanation / Answer
1)non pipelined: 250+350+150+300+200 = 1250 ps (addition of all the stages).
pipelined : 350ps.
2) non pipelined: 1250ps
ppipelined: 5*350= 1750ps(lw instruction takes 5 cycles).
3) split the longest stage i.e. ID stage into 2 stage = 350/2= 175ps.
new clock cycle will be 300ps.
4) sum of ldur and sdur= 20+15=30%
5)sumof alu and ldur= 45+20= 65%
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