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sive).&nbsp;So,&nbsp;although&nbsp;the&nbsp;initial&nbsp;design&nbsp;is&nbsp;often&nbsp;not&nbsp;in&nbsp;the&nbsp;critical&nbsp;path&nbsp;to&nbsp;&nbsp;<br />
product&nbsp;deployment,&nbsp;redesign&nbsp;of&nbsp;the&nbsp;computer&nbsp;system&nbsp;may&nbsp;need&nbsp;to&nbsp;be&nbsp;done&nbsp;quic&nbsp;<br />
kly&nbsp;to&nbsp;resolve&nbsp;problems.&nbsp;<br />
Design&nbsp;challenge:&nbsp;<br />
·&nbsp;Rapid&nbsp;redesign&nbsp;to&nbsp;accommodate&nbsp;changing&nbsp;form&nbsp;factors,&nbsp;control&nbsp;algorithms,&nbsp;&nbsp;<br />
and&nbsp;functionality&nbsp;requirements.&nbsp;<br />
6.3.&nbsp;Product&nbsp;families&nbsp;<br />
In&nbsp;many&nbsp;cases&nbsp;embedded&nbsp;system&nbsp;designs&nbsp;are&nbsp;not&nbsp;unique,&nbsp;and&nbsp;there&nbsp;are&nbsp;a&nbsp;variet&nbsp;<br />
y&nbsp;of&nbsp;systems&nbsp;of&nbsp;various&nbsp;prices&nbsp;and&nbsp;capabilities&nbsp;forming&nbsp;a&nbsp;product&nbsp;family.&nbsp;To&nbsp;<br />
&nbsp;the&nbsp;extent&nbsp;that&nbsp;system&nbsp;designers&nbsp;can&nbsp;reuse&nbsp;components,&nbsp;they&nbsp;lower&nbsp;the&nbsp;total&nbsp;<br />
&nbsp;cost&nbsp;of&nbsp;all&nbsp;systems&nbsp;in&nbsp;the&nbsp;product&nbsp;family.&nbsp;<br />
However,&nbsp;there&nbsp;is&nbsp;a&nbsp;dynamic&nbsp;tension&nbsp;between&nbsp;overly&nbsp;general&nbsp;solutions&nbsp;that&nbsp;sa&nbsp;<br />
tisfy&nbsp;a&nbsp;large&nbsp;number&nbsp;of&nbsp;niche&nbsp;requirements,&nbsp;and&nbsp;specifically&nbsp;optimized&nbsp;desig&nbsp;<br />
ns&nbsp;for&nbsp;each&nbsp;point&nbsp;in&nbsp;a&nbsp;product&nbsp;family&nbsp;space.&nbsp;Also,&nbsp;there&nbsp;may&nbsp;be&nbsp;cases&nbsp;in&nbsp;whi&nbsp;<br />
ch&nbsp;contradictory&nbsp;requirements&nbsp;between&nbsp;similar&nbsp;systems&nbsp;prevent&nbsp;the&nbsp;use&nbsp;of&nbsp;a&nbsp;s&nbsp;<br />
ingle&nbsp;subsystem&nbsp;design.&nbsp;In&nbsp;the&nbsp;Mission&nbsp;Critical&nbsp;and&nbsp;Small&nbsp;examples&nbsp;different&nbsp;<br />
&nbsp;customers&nbsp;require&nbsp;different&nbsp;interfaces&nbsp;between&nbsp;the&nbsp;embedded&nbsp;system&nbsp;and&nbsp;thei&nbsp;<br />
r&nbsp;equipment.&nbsp;In&nbsp;the&nbsp;Distributed&nbsp;example&nbsp;regulatory&nbsp;agencies&nbsp;impose&nbsp;different&nbsp;<br />
&nbsp;safety-critical&nbsp;behavior&nbsp;requirements&nbsp;depending&nbsp;on&nbsp;the&nbsp;geographic&nbsp;area&nbsp;in&nbsp;w&nbsp;<br />
hich&nbsp;the&nbsp;system&nbsp;is&nbsp;deployed.&nbsp;<br />
Design&nbsp;challenge:&nbsp;<br />
·&nbsp;Customize&nbsp;designs&nbsp;while&nbsp;minimizing&nbsp;component&nbsp;variant&nbsp;proliferation.&nbsp;<br />
7.&nbsp;Design&nbsp;culture&nbsp;<br />
Design&nbsp;is&nbsp;a&nbsp;social&nbsp;activity&nbsp;as&nbsp;well&nbsp;as&nbsp;a&nbsp;technical&nbsp;activity.&nbsp;The&nbsp;design&nbsp;of&nbsp;d&nbsp;<br />
esktop&nbsp;computers,&nbsp;and&nbsp;CPUs&nbsp;in&nbsp;particular,&nbsp;has&nbsp;matured&nbsp;in&nbsp;terms&nbsp;of&nbsp;becoming&nbsp;m&nbsp;<br />
ore&nbsp;quantitative&nbsp;in&nbsp;recent&nbsp;years.&nbsp;With&nbsp;this&nbsp;new&nbsp;maturity&nbsp;has&nbsp;come&nbsp;an&nbsp;emphasi&nbsp;<br />
s&nbsp;on&nbsp;simulation&nbsp;and&nbsp;CAD&nbsp;tools&nbsp;to&nbsp;provide&nbsp;engineering&nbsp;tradeoffs&nbsp;based&nbsp;on&nbsp;accu&nbsp;<br />
rate&nbsp;performance&nbsp;and&nbsp;cost&nbsp;predictions.&nbsp;<br />
Computer&nbsp;designers&nbsp;venturing&nbsp;into&nbsp;the&nbsp;embedded&nbsp;arena&nbsp;must&nbsp;realize&nbsp;that&nbsp;their&nbsp;<br />
&nbsp;culture&nbsp;(and&nbsp;the&nbsp;underlying&nbsp;tool&nbsp;infrastructure)&nbsp;are&nbsp;unlike&nbsp;what&nbsp;is&nbsp;commonl&nbsp;<br />
y&nbsp;practiced&nbsp;in&nbsp;some&nbsp;other&nbsp;engineering&nbsp;disciplines.&nbsp;But,&nbsp;because&nbsp;embedded&nbsp;sys&nbsp;<br />
tem&nbsp;design&nbsp;requires&nbsp;a&nbsp;confluence&nbsp;of&nbsp;engineering&nbsp;skills,&nbsp;successful&nbsp;computer&nbsp;&nbsp;<br />
designers&nbsp;and&nbsp;design&nbsp;methodologies&nbsp;must&nbsp;find&nbsp;a&nbsp;harmonious&nbsp;compromise&nbsp;with&nbsp;th&nbsp;<br />
e&nbsp;techniques&nbsp;and&nbsp;methodologies&nbsp;of&nbsp;other&nbsp;disciplines&nbsp;as&nbsp;well&nbsp;as&nbsp;company&nbsp;manag&nbsp;<br />
ement.&nbsp;Also,&nbsp;in&nbsp;many&nbsp;cases&nbsp;the&nbsp;engineers&nbsp;building&nbsp;embedded&nbsp;computer&nbsp;systems&nbsp;&nbsp;<br />
are&nbsp;not&nbsp;actually&nbsp;trained&nbsp;in&nbsp;computer&nbsp;engineering&nbsp;(or,&nbsp;perhaps&nbsp;not&nbsp;even&nbsp;elect&nbsp;<br />
rical&nbsp;engineering),&nbsp;and&nbsp;so&nbsp;are&nbsp;not&nbsp;attuned&nbsp;to&nbsp;the&nbsp;culture&nbsp;and&nbsp;methodologies&nbsp;&nbsp;<br />
of&nbsp;desktop&nbsp;computer&nbsp;design.&nbsp;<br />
7.1.&nbsp;Computer&nbsp;culture&nbsp;vs.&nbsp;other&nbsp;cultures&nbsp;<br />
A&nbsp;specific&nbsp;problem&nbsp;is&nbsp;that&nbsp;computer&nbsp;design&nbsp;tools&nbsp;have&nbsp;progressed&nbsp;to&nbsp;the&nbsp;poin&nbsp;<br />
t&nbsp;that&nbsp;many&nbsp;believe&nbsp;it&nbsp;is&nbsp;more&nbsp;cost-effective&nbsp;to&nbsp;do&nbsp;extensive&nbsp;simulation&nbsp;tha&nbsp;<br />
n&nbsp;build&nbsp;successive&nbsp;prototypes.&nbsp;However,&nbsp;in&nbsp;the&nbsp;mechanical&nbsp;arena&nbsp;much&nbsp;existin&nbsp;<br />
g&nbsp;practice&nbsp;strongly&nbsp;favors&nbsp;prototyping&nbsp;with&nbsp;less&nbsp;exhaustive&nbsp;up-front&nbsp;analysi&nbsp;<br />
s.&nbsp;Thus,&nbsp;it&nbsp;may&nbsp;be&nbsp;difficult&nbsp;to&nbsp;convince&nbsp;project&nbsp;managers&nbsp;(who&nbsp;may&nbsp;be&nbsp;applic&nbsp;<br />
ation&nbsp;area&nbsp;specialists&nbsp;rather&nbsp;than&nbsp;computer&nbsp;specialists)&nbsp;to&nbsp;spend&nbsp;limited&nbsp;ca&nbsp;<br />
pital&nbsp;budgets&nbsp;on&nbsp;CAD&nbsp;tools&nbsp;and&nbsp;defer&nbsp;the&nbsp;gratification&nbsp;of&nbsp;early&nbsp;prototype&nbsp;de&nbsp;<br />
velopment&nbsp;in&nbsp;favor&nbsp;of&nbsp;simulation.&nbsp;<br />
Design&nbsp;challenge:&nbsp;<br />
·&nbsp;Make&nbsp;simulation-based&nbsp;computer&nbsp;design&nbsp;accessible&nbsp;to&nbsp;non-specialists.&nbsp;<br />
7.2.&nbsp;Accounting&nbsp;for&nbsp;cost&nbsp;of&nbsp;engineering&nbsp;design&nbsp;<br />
One&nbsp;area&nbsp;of&nbsp;common&nbsp;concern&nbsp;is&nbsp;the&nbsp;effectiveness&nbsp;of&nbsp;using&nbsp;engineers&nbsp;in&nbsp;any&nbsp;de&nbsp;<br />
sign&nbsp;discipline.&nbsp;But,&nbsp;some&nbsp;computer&nbsp;design&nbsp;CAD&nbsp;tools&nbsp;are&nbsp;very&nbsp;expensive,&nbsp;and&nbsp;<br />
&nbsp;in&nbsp;general&nbsp;organizations&nbsp;have&nbsp;difficulty&nbsp;trading&nbsp;off&nbsp;capital&nbsp;and&nbsp;tool&nbsp;costs&nbsp;<br />
&nbsp;against&nbsp;engineering&nbsp;time.&nbsp;This&nbsp;means&nbsp;that&nbsp;computer&nbsp;designers&nbsp;may&nbsp;be&nbsp;deprive&nbsp;<br />
d&nbsp;of&nbsp;CAD&nbsp;tools&nbsp;that&nbsp;would&nbsp;reduce&nbsp;the&nbsp;total&nbsp;cost&nbsp;of&nbsp;designing&nbsp;a&nbsp;system.&nbsp;<br />
Also,&nbsp;in&nbsp;high-volume&nbsp;applications&nbsp;engineering&nbsp;costs&nbsp;can&nbsp;be&nbsp;relatively&nbsp;small&nbsp;&nbsp;<br />
when&nbsp;compared&nbsp;to&nbsp;production&nbsp;costs.&nbsp;Often,&nbsp;the&nbsp;number&nbsp;of&nbsp;engineers&nbsp;is&nbsp;fixed,&nbsp;&nbsp;<br />
and&nbsp;book-kept&nbsp;as&nbsp;a&nbsp;constant&nbsp;expense&nbsp;that&nbsp;is&nbsp;decoupled&nbsp;from&nbsp;the&nbsp;profitability&nbsp;<br />
&nbsp;of&nbsp;any&nbsp;particular&nbsp;system&nbsp;design,&nbsp;as&nbsp;is&nbsp;the&nbsp;case&nbsp;in&nbsp;all&nbsp;four&nbsp;example&nbsp;systems&nbsp;<br />
.&nbsp;This&nbsp;can&nbsp;be&nbsp;referred&nbsp;to&nbsp;as&nbsp;the&nbsp;&quot;Engineers&nbsp;Are&nbsp;Free&quot;&nbsp;syndrome.&nbsp;But,&nbsp;while&nbsp;t&nbsp;<br />
he&nbsp;cost&nbsp;of&nbsp;engineering&nbsp;time&nbsp;may&nbsp;have&nbsp;a&nbsp;small&nbsp;impact&nbsp;on&nbsp;product&nbsp;costs,&nbsp;the&nbsp;un&nbsp;<br />
availability&nbsp;of&nbsp;enough&nbsp;engineers&nbsp;to&nbsp;do&nbsp;work&nbsp;on&nbsp;all&nbsp;the&nbsp;products&nbsp;being&nbsp;design&nbsp;<br />
ed&nbsp;can&nbsp;have&nbsp;a&nbsp;significant&nbsp;opportunity&nbsp;cost&nbsp;(which&nbsp;is,&nbsp;in&nbsp;general,&nbsp;unmeasured&nbsp;<br />
).&nbsp;<br />
Design&nbsp;challenge:&nbsp;<br />
·&nbsp;Improved&nbsp;productivity&nbsp;via&nbsp;using&nbsp;tools&nbsp;and&nbsp;methodologies&nbsp;may&nbsp;be&nbsp;better&nbsp;rec&nbsp;<br />
eived&nbsp;by&nbsp;managers&nbsp;if&nbsp;it&nbsp;is&nbsp;perceived&nbsp;to&nbsp;increase&nbsp;the&nbsp;number&nbsp;of&nbsp;products&nbsp;that&nbsp;<br />
&nbsp;can&nbsp;be&nbsp;designed,&nbsp;rather&nbsp;than&nbsp;merely&nbsp;the&nbsp;efficiency&nbsp;of&nbsp;engineers&nbsp;on&nbsp;any&nbsp;give&nbsp;<br />
n&nbsp;product&nbsp;design&nbsp;effort.&nbsp;This&nbsp;is&nbsp;a&nbsp;subtle&nbsp;but,&nbsp;in&nbsp;practice,&nbsp;important&nbsp;distin&nbsp;<br />
ction.&nbsp;<br />
7.3.&nbsp;Inertia&nbsp;<br />
In&nbsp;general,&nbsp;the&nbsp;cost&nbsp;of&nbsp;change&nbsp;in&nbsp;an&nbsp;organization&nbsp;is&nbsp;high&nbsp;both&nbsp;in&nbsp;terms&nbsp;of&nbsp;m&nbsp;<br />
oney&nbsp;and&nbsp;organizational&nbsp;disruption.&nbsp;The&nbsp;computer&nbsp;industry&nbsp;can&nbsp;be&nbsp;thought&nbsp;of&nbsp;&nbsp;<br />
as&nbsp;being&nbsp;forced&nbsp;to&nbsp;change&nbsp;by&nbsp;inexorable&nbsp;exponential&nbsp;growth&nbsp;in&nbsp;hardware&nbsp;capab&nbsp;<br />
ilities.&nbsp;However,&nbsp;the&nbsp;impact&nbsp;of&nbsp;this&nbsp;growth&nbsp;seems&nbsp;to&nbsp;have&nbsp;been&nbsp;delayed&nbsp;in&nbsp;em&nbsp;<br />
bedded&nbsp;system&nbsp;development.&nbsp;In&nbsp;part&nbsp;this&nbsp;is&nbsp;because&nbsp;of&nbsp;the&nbsp;long&nbsp;time&nbsp;that&nbsp;ela&nbsp;<br />
pses&nbsp;between&nbsp;new&nbsp;technology&nbsp;introduction&nbsp;and&nbsp;wide-scale&nbsp;use&nbsp;in&nbsp;inexpensive&nbsp;s&nbsp;<br />
ystems.&nbsp;Thus,&nbsp;it&nbsp;may&nbsp;simply&nbsp;be&nbsp;that&nbsp;complex&nbsp;designs&nbsp;will&nbsp;force&nbsp;updated&nbsp;CAD&nbsp;t&nbsp;<br />
ools&nbsp;and&nbsp;design&nbsp;methodologies&nbsp;to&nbsp;be&nbsp;adopted&nbsp;for&nbsp;embedded&nbsp;systems&nbsp;in&nbsp;the&nbsp;near&nbsp;<br />
&nbsp;future.&nbsp;<br />
On&nbsp;the&nbsp;other&nbsp;hand,&nbsp;the&nbsp;latest&nbsp;computer&nbsp;design&nbsp;technologies&nbsp;may&nbsp;not&nbsp;have&nbsp;been&nbsp;<br />
&nbsp;adopted&nbsp;by&nbsp;many&nbsp;embedded&nbsp;system&nbsp;makers&nbsp;because&nbsp;they&nbsp;aren't&nbsp;necessary.&nbsp;Tool&nbsp;&nbsp;<br />
development&nbsp;that&nbsp;concentrates&nbsp;on&nbsp;the&nbsp;ability&nbsp;to&nbsp;handle&nbsp;millions&nbsp;of&nbsp;transisto&nbsp;<br />
rs&nbsp;may&nbsp;simply&nbsp;not&nbsp;be&nbsp;relevant&nbsp;to&nbsp;designers&nbsp;of&nbsp;systems&nbsp;using&nbsp;4-&nbsp;and&nbsp;8-bit&nbsp;mic&nbsp;<br />
roprocessors&nbsp;that&nbsp;constitute&nbsp;the&nbsp;bulk&nbsp;of&nbsp;the&nbsp;embedded&nbsp;CPU&nbsp;market.&nbsp;And,&nbsp;even&nbsp;&nbsp;<br />
if&nbsp;they&nbsp;are&nbsp;useful,&nbsp;the&nbsp;need&nbsp;for&nbsp;them&nbsp;may&nbsp;not&nbsp;be&nbsp;compelling&nbsp;enough&nbsp;to&nbsp;justif&nbsp;<br />
y&nbsp;the&nbsp;pain&nbsp;and&nbsp;up-front&nbsp;expense&nbsp;of&nbsp;change&nbsp;so&nbsp;long&nbsp;as&nbsp;older&nbsp;techniques&nbsp;work.&nbsp;<br />
That&nbsp;is&nbsp;not&nbsp;to&nbsp;say&nbsp;that&nbsp;new&nbsp;tools&nbsp;aren't&nbsp;needed,&nbsp;but&nbsp;rather&nbsp;that&nbsp;the&nbsp;force&nbsp;o&nbsp;<br />
f&nbsp;cultural&nbsp;inertia&nbsp;will&nbsp;only&nbsp;permit&nbsp;adoption&nbsp;of&nbsp;low-cost&nbsp;tools&nbsp;with&nbsp;signific&nbsp;<br />
ant&nbsp;advantages&nbsp;to&nbsp;the&nbsp;problem&nbsp;at&nbsp;hand.&nbsp;<br />
Design&nbsp;challenge:&nbsp;<br />
·&nbsp;Find/create&nbsp;design&nbsp;tools&nbsp;and&nbsp;methodologies&nbsp;that&nbsp;provide&nbsp;unique,&nbsp;compellin&nbsp;<br />
g&nbsp;advantages&nbsp;for&nbsp;embedded&nbsp;design.&nbsp;<br />
8.&nbsp;Conclusions&nbsp;<br />
Many&nbsp;embedded&nbsp;systems&nbsp;have&nbsp;requirements&nbsp;that&nbsp;differ&nbsp;significantly&nbsp;both&nbsp;in&nbsp;de&nbsp;<br />
tails&nbsp;and&nbsp;in&nbsp;scope&nbsp;from&nbsp;desktop&nbsp;computers.&nbsp;In&nbsp;particular,&nbsp;the&nbsp;demands&nbsp;of&nbsp;the&nbsp;<br />
&nbsp;specific&nbsp;application&nbsp;and&nbsp;the&nbsp;interface&nbsp;with&nbsp;external&nbsp;equipment&nbsp;may&nbsp;dominate&nbsp;<br />
&nbsp;the&nbsp;system&nbsp;design.&nbsp;Also,&nbsp;long&nbsp;life-cycles&nbsp;and&nbsp;in&nbsp;some&nbsp;cases&nbsp;extreme&nbsp;cost&nbsp;se&nbsp;<br />
nsitivity&nbsp;require&nbsp;more&nbsp;attention&nbsp;to&nbsp;optimization&nbsp;based&nbsp;on&nbsp;these&nbsp;goals&nbsp;rather&nbsp;<br />
&nbsp;than&nbsp;maximizing&nbsp;the&nbsp;computational&nbsp;throughput.&nbsp;<br />
The&nbsp;business&nbsp;and&nbsp;cultural&nbsp;climates&nbsp;in&nbsp;many&nbsp;embedded&nbsp;system&nbsp;design&nbsp;situations&nbsp;<br />
&nbsp;are&nbsp;such&nbsp;that&nbsp;traditional&nbsp;simulation-based&nbsp;computer&nbsp;design&nbsp;techniques&nbsp;may&nbsp;n&nbsp;<br />
ot&nbsp;be&nbsp;viable&nbsp;in&nbsp;their&nbsp;current&nbsp;form.&nbsp;Such&nbsp;methodologies&nbsp;may&nbsp;not&nbsp;be&nbsp;cost-effec&nbsp;<br />
tive&nbsp;given&nbsp;constraints&nbsp;on&nbsp;categories&nbsp;of&nbsp;expenditures,&nbsp;may&nbsp;not&nbsp;be&nbsp;seen&nbsp;as&nbsp;wor&nbsp;<br />
thwhile&nbsp;by&nbsp;non-computer-trained&nbsp;professionals,&nbsp;or&nbsp;may&nbsp;simply&nbsp;be&nbsp;solving&nbsp;the&nbsp;&nbsp;<br />
wrong&nbsp;problems.&nbsp;<br />
Recent&nbsp;interest&nbsp;in&nbsp;hardware/software&nbsp;codesign&nbsp;is&nbsp;a&nbsp;step&nbsp;in&nbsp;the&nbsp;right&nbsp;directi&nbsp;<br />
on,&nbsp;as&nbsp;it&nbsp;permits&nbsp;tradeoffs&nbsp;between&nbsp;hardware&nbsp;and&nbsp;software&nbsp;that&nbsp;are&nbsp;critical&nbsp;&nbsp;<br />
for&nbsp;more&nbsp;cost-effective&nbsp;embedded&nbsp;systems.&nbsp;However,&nbsp;to&nbsp;be&nbsp;successful&nbsp;future&nbsp;t&nbsp;<br />
ools&nbsp;may&nbsp;well&nbsp;need&nbsp;to&nbsp;increase&nbsp;scope&nbsp;even&nbsp;further&nbsp;to&nbsp;include&nbsp;life-cycle&nbsp;issu&nbsp;<br />
es&nbsp;and&nbsp;business&nbsp;issues.&nbsp;<br />
The&nbsp;tutorial&nbsp;slide&nbsp;presentation&nbsp;presented&nbsp;at&nbsp;the&nbsp;conference&nbsp;augments&nbsp;this&nbsp;pa&nbsp;<br />
per,&nbsp;and&nbsp;may&nbsp;be&nbsp;found&nbsp;at:&nbsp;<a href="http://www.cs.cmu.edu/~koopman/iccd96">http://www.cs.cmu.edu/~koopman/iccd96</a>&nbsp;<br />
&nbsp;<br />
--&nbsp;<br />
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