<s>
Commodity	B-Device
computing	I-Device
(	O
also	O
known	O
as	O
commodity	B-Operating_System
cluster	I-Operating_System
computing	O
)	O
involves	O
the	O
use	O
of	O
large	O
numbers	O
of	O
already-available	O
computing	O
components	O
for	O
parallel	B-Operating_System
computing	I-Operating_System
,	O
to	O
get	O
the	O
greatest	O
amount	O
of	O
useful	O
computation	O
at	O
low	O
cost	O
.	O
</s>
<s>
It	O
is	O
computing	O
done	O
in	O
commodity	B-Device
computers	I-Device
as	O
opposed	O
to	O
in	O
high-cost	O
superminicomputers	B-Device
or	O
in	O
boutique	O
computers	O
.	O
</s>
<s>
Commodity	B-Device
computers	I-Device
are	O
computer	O
systems	O
-	O
manufactured	O
by	O
multiple	O
vendors	O
-	O
incorporating	O
components	O
based	O
on	O
open	O
standards	O
.	O
</s>
<s>
A	O
governing	O
principle	O
of	O
commodity	B-Device
computing	I-Device
is	O
that	O
it	O
is	O
preferable	O
to	O
have	O
more	O
low-performance	O
,	O
low-cost	O
hardware	O
working	O
in	O
parallel	O
(	O
scalar	O
computing	O
)	O
(	O
e.g.	O
</s>
<s>
AMD	O
x86	B-Operating_System
CISC	B-Architecture
)	O
than	O
to	O
have	O
fewer	O
high-performance	O
,	O
high-cost	O
hardware	O
items	O
(	O
e.g.	O
</s>
<s>
IBM	O
POWER7	B-Device
or	O
Sun-Oracle	O
'	O
s	O
SPARC	B-Architecture
RISC	B-Architecture
)	O
.	O
</s>
<s>
At	O
some	O
point	O
,	O
the	O
number	O
of	O
discrete	O
systems	O
in	O
a	O
cluster	O
will	O
be	O
greater	O
than	O
the	O
mean	O
time	O
between	O
failures	O
(	O
MTBF	O
)	O
for	O
any	O
hardware	O
platform	O
,	O
no	O
matter	O
how	O
reliable	O
,	O
so	O
fault	B-General_Concept
tolerance	I-General_Concept
must	O
be	O
built	O
into	O
the	O
controlling	O
software	O
.	O
</s>
<s>
The	O
move	O
towards	O
commodity	B-Device
computing	I-Device
began	O
when	O
DEC	O
introduced	O
the	O
PDP-8	B-Device
in	O
1965	O
.	O
</s>
<s>
The	O
entire	O
minicomputer	B-Architecture
industry	O
sprang	O
up	O
to	O
supply	O
the	O
demand	O
for	O
'	O
small	O
 '	O
computers	O
like	O
the	O
PDP-8	B-Device
.	O
</s>
<s>
Unfortunately	O
,	O
each	O
of	O
the	O
many	O
different	O
brands	O
of	O
minicomputers	B-Architecture
had	O
to	O
stand	O
on	O
its	O
own	O
because	O
there	O
was	O
no	O
software	O
and	O
very	O
little	O
hardware	O
compatibility	O
between	O
the	O
brands	O
.	O
</s>
<s>
When	O
the	O
first	O
general	O
purpose	O
microprocessor	B-Architecture
was	O
introduced	O
in	O
1971	O
(	O
Intel	B-General_Concept
4004	I-General_Concept
)	O
it	O
immediately	O
began	O
chipping	O
away	O
at	O
the	O
low	O
end	O
of	O
the	O
computer	O
market	O
,	O
replacing	O
embedded	B-Architecture
minicomputers	I-Architecture
in	O
many	O
industrial	O
devices	O
.	O
</s>
<s>
This	O
process	O
accelerated	O
in	O
1977	O
with	O
the	O
introduction	O
of	O
the	O
first	O
commodity-like	O
microcomputer	O
,	O
the	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
With	O
the	O
development	O
of	O
the	O
VisiCalc	B-Application
application	O
in	O
1979	O
,	O
microcomputers	O
broke	O
out	O
of	O
the	O
factory	O
and	O
began	O
entering	O
office	O
suites	O
in	O
large	O
quantities	O
,	O
but	O
still	O
through	O
the	O
back	O
door	O
.	O
</s>
<s>
The	O
IBM	B-Device
PC	I-Device
was	O
introduced	O
in	O
1981	O
and	O
immediately	O
began	O
displacing	O
Apple	B-Device
IIs	I-Device
in	O
the	O
corporate	O
world	O
,	O
but	O
commodity	B-Device
computing	I-Device
as	O
we	O
know	O
it	O
today	O
truly	O
began	O
when	O
Compaq	O
developed	O
the	O
first	O
true	O
IBM	B-Device
PC	I-Device
compatible	O
.	O
</s>
<s>
More	O
and	O
more	O
PC-compatible	O
microcomputers	O
began	O
coming	O
into	O
big	O
companies	O
through	O
the	O
front	O
door	O
and	O
commodity	B-Device
computing	I-Device
was	O
well	O
established	O
.	O
</s>
<s>
At	O
first	O
,	O
price	O
was	O
the	O
key	O
justification	O
but	O
by	O
the	O
late	O
1980s	O
and	O
early	O
1990s	O
,	O
VLSI	O
semiconductor	O
technology	O
had	O
evolved	O
to	O
the	O
point	O
where	O
microprocessor	B-Architecture
performance	O
began	O
to	O
eclipse	O
the	O
performance	O
of	O
discrete	O
logic	O
designs	O
.	O
</s>
<s>
These	O
traditional	O
designs	O
were	O
limited	O
by	O
speed-of-light	O
delay	O
issues	O
inherent	O
in	O
any	O
CPU	O
larger	O
than	O
a	O
single	O
chip	O
,	O
and	O
performance	O
alone	O
began	O
driving	O
the	O
success	O
of	O
microprocessor-based	O
systems	O
.	O
</s>
<s>
By	O
the	O
mid-1990s	O
,	O
nearly	O
all	O
computers	O
made	O
were	O
based	O
on	O
microprocessors	B-Architecture
,	O
and	O
the	O
majority	O
of	O
general	O
purpose	O
microprocessors	B-Architecture
were	O
implementations	O
of	O
the	O
x86	B-Operating_System
instruction	O
set	O
architecture	O
.	O
</s>
<s>
Today	O
,	O
there	O
are	O
fewer	O
and	O
fewer	O
general	O
business	O
computing	O
requirements	O
that	O
cannot	O
be	O
met	O
with	O
off-the-shelf	O
commodity	B-Device
computers	I-Device
.	O
</s>
<s>
Yahoo	B-Application
!	I-Application
</s>
