<s>
A	O
channel	B-Algorithm
router	I-Algorithm
is	O
a	O
specific	O
variety	O
of	O
router	B-Algorithm
for	I-Algorithm
integrated	I-Algorithm
circuits	I-Algorithm
.	O
</s>
<s>
Normally	O
using	O
two	O
layers	O
of	O
interconnect	B-Architecture
,	O
it	O
must	O
connect	O
the	O
specified	O
pins	O
on	O
the	O
top	O
and	O
bottom	O
of	O
the	O
channel	O
.	O
</s>
<s>
The	O
height	O
of	O
the	O
channel	O
is	O
not	O
specified	O
-	O
the	O
router	B-Algorithm
computes	O
what	O
height	O
is	O
needed	O
.	O
</s>
<s>
Channel	B-Algorithm
routers	I-Algorithm
were	O
one	O
of	O
the	O
first	O
forms	O
of	O
routers	B-Algorithm
for	O
integrated	O
circuits	O
,	O
and	O
were	O
heavily	O
used	O
for	O
many	O
years	O
,	O
with	O
YACR	O
perhaps	O
the	O
best	O
known	O
program	O
.	O
</s>
<s>
However	O
,	O
modern	O
chips	O
have	O
many	O
more	O
than	O
2	O
interconnect	B-Architecture
layers	O
.	O
</s>
<s>
Although	O
the	O
effort	O
was	O
made	O
to	O
extend	O
channel	B-Algorithm
routers	I-Algorithm
to	O
more	O
layers	O
,	O
this	O
approach	O
was	O
never	O
very	O
popular	O
,	O
since	O
it	O
did	O
not	O
work	O
well	O
with	O
over-the-cell	O
routing	B-Algorithm
where	O
pins	O
are	O
not	O
movable	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
area	O
routers	B-Algorithm
have	O
in	O
general	O
taken	O
over	O
.	O
</s>
