Lecture 03 - computer organization and architecture

8/12/2019 Lecture 03 - computer organization and architecture

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Lecture 3

CMPT215.3


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Performance


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Chapter 1 Computer Abstractions and Technology 4

Understanding Performance

Algorithm Determines number of oerations e!ecuted

Programming language" comiler" architecture Determine number of machine instructions e!ecuted er

oeration

Processor and memor# s#stem Determine ho$ fast instructions are e!ecuted

%&' s#stem (including ')*

Determines ho$ fast %&' oerations are e!ecuted


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+esonse Time and Throughut

+esonse time ,o$ long it ta-es to do a tas-

Throughut Total $or- done er unit time

e.g." tas-s&transactions& er hour

,o$ are resonse time and throughut affected b# +elacing the rocessor $ith a faster /ersion0

Adding more rocessors0

ell focus on resonse time for no$


5/35Chapter 1 Computer Abstractions and Technology 6

+elati/e Performance

Define Performance 1&4!ecution Time

6 is ntime faster than 78

n== 67

76

time4!ecutiontime4!ecution

ePerformancePerformanc

4!amle9 time ta-en to run a rogram 1:s on A" 15s on ;

4!ecution Time;& 4!ecution TimeA 15s & 1:s 1.5

)o A is 1.5 times faster than ;


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Measuring 4!ecution Time

4lased time Total resonse time" including all asects

Processing" %&'" ') o/erhead" idle time

Determines s#stem erformance

CPU time Time sent rocessing a gi/en


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CPU Time

Performance imro/ed b# +educing number of cloc- c#cles

%ncreasing cloc- rate

,ard$are designer must often trade off cloc- rateagainst c#cle count

+ateCloc-

C#clesCloc-CPU

TimeC#cleCloc-C#clesCloc-CPUTimeCPU

=

=


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CPU Cloc-ing

'eration of digital hard$are go/erned b# a

constant=rate cloc-

Cloc- (c#cles*

Data transfer

and comutation

Udate state

Cloc- eriod

Cloc- eriod9 duration of a cloc- c#cle e.g." 25:s :.25ns 25:>1:?12s

Cloc- fre@uenc# (rate*9 c#cles er second e.g." .:B, :::M, .:>1:,


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CPU Time 4!amle

Comuter A9 2B, cloc-" 1:s CPU time

Designing Comuter ; Aim for Es CPU time

Can do faster cloc-" but causes 1.2 > cloc- c#cles

,o$ fast must Comuter ; cloc- be0

B,Es

1:2

Es

1:2:1.2+ateCloc-

1:2:2B,1:s

+ateCloc-TimeCPUC#clesCloc-

Es

C#clesCloc-1.2

TimeCPU

C#clesCloc-+ateCloc-

DD

;

D

AAA

A

;

;;

=

=

=

==

=

==


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%nstruction Count and CP%

%nstruction Count for a rogram Determined b# rogram" %)A and comiler

A/erage c#cles er instruction Determined b# CPU hard$are

%f different instructions ha/e different CP% A/erage CP% affected b# instruction mi!

+ateCloc-

CP%Countn%nstructio

TimeC#cleCloc-CP%Countn%nstructioTimeCPUn%nstructioerC#clesCountn%nstructioC#clesCloc-

=

==


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CP% 4!amle

Comuter A9 C#cle Time 25:s" CP% 2.: Comuter ;9 C#cle Time 5::s" CP% 1.2 )ame %)A hich is faster" and b# ho$ much0

1.25::s%

E::s%

ATimeCPU

;TimeCPU

E::s%5::s1.2%

;TimeC#cle

;CP%Countn%nstructio

;TimeCPU

5::s%25:s2.:%

ATimeC#cleACP%Countn%nstructioATimeCPU

=

=

==

=

==

=

A is faster

b# this much


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Chapter 1 Computer Abstractions and Technology 1!

CP% in More Detail

%f different instruction classes ta-e different

numbers of c#cles

=

=n

1i

ii *Countn%nstructio(CP%C#clesCloc-

eighted a/erage CP%

=

==

n

1i

i

i Countn%nstructio

Countn%nstructio

CP%Countn%nstructio

C#clesCloc-

CP%

+elati/e fre@uenc#


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CP% 4!amle

Alternati/e comiled code se@uences using

instructions in classes A" ;" C

Class A ; C

CP% for class 1 2 3

%C in se@uence 1 2 1 2

%C in se@uence 2 1 1

)e@uence 19 %C 5

Cloc- C#cles 2>1 F 1>2 F 2>3

1:

A/g. CP% 1:&5 2.:

)e@uence 29 %C E

Cloc- C#cles >1 F 1>2 F 1>3

A/g. CP% &E 1.5


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Performance )ummar#

Performance deends on Algorithm9 affects %C" ossibl# CP%

Programming language9 affects %C" CP%

Comiler9 affects %C" CP%

%nstruction set architecture9 affects %C" CP%" Tc

The BIG Picture

c#cleCloc-

)econds

n%nstructio

c#clesCloc-

Program

ns%nstructioTimeCPU =

G1


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Pitfall9 Amdahls La$

%mro/ing an asect of a comuter and e!ecting a

roortional imro/ement in o/erall erformance

1.HIallacies

a

ndPitfalls

2:H:

2: +=n

Cant be doneJ

unaffectedaffected

imro/ed T

factortimro/emen

TT +=

4!amle9 multil# accounts for H:s&1::s ,o$ much imro/ement in multil# erformance to get 5>

o/erall0

Corollar#9 ma-e the common case fast


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)P4C CPU ;enchmar- Programs used to measure erformance

)uosedl# t#ical of actual $or-load )tandard Performance 4/aluation Cor ()P4C*

De/elos benchmar-s for CPU" %&'" eb"

)P4C CPU2::E

4lased time to e!ecute a selection of rograms Kegligible %&'" so focuses on CPU erformance

Kormalie relati/e to reference machine )ummarie as geometric mean of erformance ratios

C%KT2::E (integer* and CIP2::E (floating=oint*

n

n

1i

iratiotime4!ecution=


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Iallac#9 Lo$ Po$er at %dle

Loo- bac- at 6 o$er benchmar- At 1:: load9 25

At 5: load9 2E (H3*

At 1: load9 1H: (E1*

Boogle data center Mostl# oerates at 1: ? 5: load

At 1:: load less than 1 of the time

Consider designing rocessors to ma-e o$erroortional to load


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Pitfall9 M%P) as a Performance Metric

M%P)9 Millions of %nstructions Per )econd Doesnt account for

Differences in %)As bet$een comuters

Differences in comle!it# bet$een instructions

EE

E

1:CP%

rateCloc-

1:rateCloc-

CP%countn%nstructio

countn%nstructio

1:time4!ecution

countn%nstructioM%P)

=

=

=

CP% /aries bet$een rograms on a gi/en CPU


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Definitions ilob#te ? 21:or 1":2 b#tes

Megab#te? 22:or 1":H"5NE b#tes sometimes rounded8 to 1:Eor 1":::"::: b#tes

Bigab#te ? 23:or 1":N3"N1"H2 b#tes

sometimes rounded to 1:Dor 1":::":::"::: b#tes

Terab#te ? 2A:

or 1":"511"E2N"NNE b#tes sometimes rounded to 1:12or 1":::":::":::"::: b#tes

Petab#te ? 25:or 1:2 terab#tes

sometimes rounded to 1:15or 1":::":::":::":::"::: b#tes

4!ab#te ? 2E:or 1:2 etab#tes

)ometimes rounded to 1:1Hor 1":::":::":::":::":::"::: b#tes

Chapter 1 Computer Abstractions and Technology


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Arithmetic

G3.


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July 16, 2014 Chapter 3 Arithmetic for Computers 24

Arithmetic for Comuters

'erations on integers Addition and subtraction

Multilication and di/ision

Dealing $ith o/erflo$

Iloating=oint real numbers +eresentation and oerations

.1%ntroductio

n

G3.


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%nteger Addition

4!amle9 N F E

2Additiona

n

d)ubtraction

'/erflo$ if result out of range Adding F/e and ?/e oerands" no o/erflo$

Adding t$o F/e oerands '/erflo$ if result sign is 1

Adding t$o ?/e oerands '/erflo$ if result sign is :


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%nteger )ubtraction

Add negation of second oerand

4!amle9 N ? E N F (?E*

FN9 :::: :::: :::: :111

?E9 1111 1111 1111 1:1:

F19 :::: :::: :::: :::1

'/erflo$ if result out of range )ubtracting t$o F/e or t$o ?/e oerands" no o/erflo$

)ubtracting F/e from ?/e oerand '/erflo$ if result sign is :

)ubtracting ?/e from F/e oerand '/erflo$ if result sign is 1


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1=bit adder

li i h fl


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Dealing $ith '/erflo$

)ome languages (e.g." C* ignore o/erflo$ Use M%P) addu" addui" subuinstructions

'ther languages (e.g." Ada" Iortran* re@uireraising an e!cetion

Use M%P)add

"addi

"sub

instructions 'n o/erflo$" in/o-e e!cetion handler )a/e PC in e!cetion rogram counter (4PC* register Oum to redefined handler address mfc0(mo/e from corocessor reg* instruction can

retrie/e 4PC /alue" to return after correcti/e action

A i h i f M l i di


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Arithmetic for Multimedia

Brahics and media rocessing oerates on

/ectors of H=bit and 1E=bit data Use E=bit adder" $ith artitioned carr# chain

'erate on H>H=bit" >1E=bit" or 2>32=bit /ectors

)%MD (single=instruction" multile=data* )aturating oerations

'n o/erflo$" result is largest reresentable /alue c.f. 2s=comlement modulo arithmetic

4.g." cliing in audio" saturation in /ideo

M l i li i

G3.3


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Multilication

)tart $ith long=multilication aroach

1000

1001

1000

00000000

1000

1001000

Length of roduct isthe sum of oerand

lengths

multilicand

multilier

roduct

3Multilicat io

n

M lti li ti , d


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Multilication ,ard$are

Initially 0

' ti i d M lti li


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'timied Multilier

Perform stes in arallel9 add&shift

'ne c#cle er artial=roduct addition Thats o-" if fre@uenc# of multilications is lo$

I t M lti li


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Iaster Multilier

Uses multile adders Cost&erformance tradeoff

Can be ielined )e/eral multilication erformed in arallel

M%P) Multilication


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M%P) Multilication

T$o 32=bit registers for roduct ,%9 most=significant 32 bits

L'9 least=significant 32=bits

%nstructions mult rs, rt / multu rs, rt

E=bit roduct in ,%&L'

mfhi rd / mflo rd Mo/e from ,%&L' to rd

Can test ,% /alue to see if roduct o/erflo$s 32 bits

mul rd, rs, rt Least=significant 32 bits of roduct ? rd

Di/ision

G3.


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Di/ision Chec- for : di/isor

Long di/ision aroach %f di/isor Q di/idend bits

1 bit in @uotient" subtract

'ther$ise : bit in @uotient" bring do$n ne!t di/idend

bit

+estoring di/ision Do the subtract" and if remainder goes R

:" add di/isor bac-

)igned di/ision Di/ide using absolute /alues

Ad


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Di/ision ,ard$are

%nitiall# di/idend

%nitiall# di/isor inleft half

M%P) Di/ision


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M%P) Di/ision

Use ,%&L' registers for result ,%9 32=bit remainder

L'9 32=bit @uotient

%nstructions

div rs, rt / divu rs, rt Ko o/erflo$ or di/ide=b#=: chec-ing

)oft$are must erform chec-s if re@uired

Use mfhi" mfloto access result


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+eferences

Patterson and ,enness# ? Comuter 'rganiation and DesignThe ,ard$are&)oft$are interface (fourth edition*

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Lecture 03 - computer organization and architecture

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