<s>
One	O
such	O
consideration	O
is	O
to	O
define	O
coherency	B-General_Concept
granules	I-General_Concept
(	O
CG	O
)	O
that	O
relate	O
to	O
units	O
of	O
data	O
that	O
are	O
stored	O
in	O
memory	O
.	O
</s>
<s>
These	O
units	O
generally	O
have	O
a	O
close	O
relationship	O
to	O
caches	B-General_Concept
that	O
may	O
be	O
used	O
in	O
the	O
system	O
.	O
</s>
<s>
The	O
Coherency	B-General_Concept
Granule	I-General_Concept
size	O
typically	O
corresponds	O
to	O
the	O
cache	B-General_Concept
line	O
size	O
in	O
a	O
computer	O
system	O
.	O
</s>
<s>
The	O
hardware	O
is	O
designed	O
with	O
the	O
assumption	O
that	O
coherency	B-General_Concept
granules	I-General_Concept
will	O
be	O
the	O
data	O
packets	O
that	O
are	O
typically	O
transferred	O
in	O
a	O
cache	B-General_Concept
coherent	I-General_Concept
system	I-General_Concept
when	O
accessing	O
coherent	O
data	O
.	O
</s>
<s>
The	O
magnitude	O
of	O
the	O
coherency	B-General_Concept
granule	I-General_Concept
is	O
typically	O
significantly	O
greater	O
than	O
the	O
bus	O
size	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
current	O
processing	O
systems	O
,	O
the	O
coherency	B-General_Concept
granule	I-General_Concept
is	O
commonly	O
32	O
bytes	O
,	O
and	O
the	O
bus	O
size	O
is	O
8	O
bytes	O
wide	O
.	O
</s>
<s>
In	O
such	O
a	O
case	O
,	O
a	O
data	O
transfer	O
of	O
one	O
coherency	B-General_Concept
granule	I-General_Concept
requires	O
4	O
cycles	O
on	O
the	O
bus	O
.	O
</s>
<s>
Thus	O
a	O
burst	O
transfer	O
of	O
a	O
coherency	B-General_Concept
granule	I-General_Concept
will	O
take	O
less	O
time	O
than	O
two	O
transfers	O
each	O
of	O
a	O
half	O
of	O
a	O
coherency	B-General_Concept
granule	I-General_Concept
.	O
</s>
<s>
As	O
systems	O
continue	O
to	O
get	O
more	O
and	O
more	O
complex	O
,	O
there	O
has	O
been	O
a	O
tendency	O
to	O
increase	O
the	O
size	O
of	O
coherency	B-General_Concept
granules	I-General_Concept
.	O
</s>
<s>
As	O
the	O
size	O
of	O
coherency	B-General_Concept
granules	I-General_Concept
increases	O
,	O
there	O
is	O
thus	O
more	O
data	O
per	O
coherency	B-General_Concept
granule	I-General_Concept
.	O
</s>
