<s>
In	O
lower	O
power	O
systems	O
,	O
Hierarchical	B-General_Concept
Value	I-General_Concept
Cache	I-General_Concept
refers	O
to	O
the	O
hierarchical	O
arrangement	O
of	O
Value	O
Caches	B-General_Concept
(	O
VCs	O
)	O
in	O
such	O
a	O
fashion	O
that	O
lower	O
level	O
VCs	O
observe	O
higher	O
hit-rates	O
,	O
but	O
undergo	O
more	O
switching	O
activity	O
on	O
VC	O
hits	O
.	O
</s>
<s>
The	O
organization	O
is	O
similar	O
to	O
Memory	B-General_Concept
Hierarchy	I-General_Concept
,	O
where	O
lower-level	O
caches	B-General_Concept
enjoy	O
higher	O
hit	O
rates	O
,	O
but	O
longer	O
hit	O
latencies	O
.	O
</s>
<s>
The	O
architecture	O
for	O
Hierarchical	B-General_Concept
Value	I-General_Concept
Cache	I-General_Concept
is	O
mainly	O
organized	O
along	O
two	O
approaches	O
:	O
Hierarchical	O
Unified	O
Value	O
Cache	B-General_Concept
(	O
HUVC	O
)	O
and	O
Hierarchical	O
Combinational	O
Value	O
Cache	B-General_Concept
(	O
HCVC	O
)	O
.	O
</s>
<s>
This	O
architecture	O
of	O
Value	O
Cache	B-General_Concept
employs	O
all	O
value	O
caches	B-General_Concept
storing	O
full	O
data	O
values	O
,	O
with	O
larger	O
value	O
caches	B-General_Concept
in	O
the	O
lower	O
levels	O
of	O
the	O
hierarchy	O
.	O
</s>
<s>
The	O
cache	B-General_Concept
in	O
HUVC	O
in	O
managed	O
by	O
LRU	O
policy	O
,	O
with	O
each	O
VC	O
storing	O
32-bit	O
values	O
.	O
</s>
<s>
For	O
incoming	O
data	O
,	O
it	O
is	O
simultaneously	O
checked	O
with	O
the	O
VC	O
on	O
each	O
level	O
,	O
with	O
the	O
uppermost	O
VC	O
hit	O
getting	O
encoded	B-Algorithm
.	O
</s>
<s>
By	O
switching	O
any	O
bit	O
of	O
32-bit	O
data	B-General_Concept
bus	I-General_Concept
,	O
we	O
can	O
get	O
(	O
32	O
!	O
)	O
/	O
((32-i )	O
!	O
i	O
!	O
)	O
</s>
<s>
For	O
easy	O
VC	O
index	O
encoding	B-Algorithm
,	O
we	O
partition	O
the	O
data	B-General_Concept
bus	I-General_Concept
into	O
i	O
segments	O
and	O
switch	O
one	O
bit	O
in	O
each	O
segment	O
.	O
</s>
<s>
For	O
4-level	O
HUVC	O
,	O
and	O
32-bit	O
data	B-General_Concept
bus	I-General_Concept
,	O
the	O
total	O
VC	O
size	O
is	O
22.4KB	O
.	O
</s>
<s>
Similar	O
to	O
the	O
HUVC	O
,	O
the	O
incoming	O
data	O
is	O
simultaneously	O
checked	O
with	O
the	O
VC	O
on	O
each	O
level	O
,	O
with	O
the	O
uppermost	O
VC	O
hit	O
getting	O
encoded	B-Algorithm
.	O
</s>
<s>
For	O
4-level	O
HCVC	O
with	O
32-bit	O
data	B-General_Concept
bus	I-General_Concept
,	O
the	O
total	O
VC	O
size	O
is	O
only	O
240	O
bytes	O
.	O
</s>
