<s>
Memory	B-General_Concept
latency	I-General_Concept
is	O
the	O
time	O
(	O
the	O
latency	O
)	O
between	O
initiating	O
a	O
request	O
for	O
a	O
byte	B-Application
or	O
word	O
in	O
memory	B-General_Concept
until	O
it	O
is	O
retrieved	O
by	O
a	O
processor	B-General_Concept
.	O
</s>
<s>
If	O
the	O
data	O
are	O
not	O
in	O
the	O
processor	B-General_Concept
's	I-General_Concept
cache	I-General_Concept
,	O
it	O
takes	O
longer	O
to	O
obtain	O
them	O
,	O
as	O
the	O
processor	B-General_Concept
will	O
have	O
to	O
communicate	O
with	O
the	O
external	O
memory	B-General_Concept
cells	O
.	O
</s>
<s>
Latency	O
is	O
therefore	O
a	O
fundamental	O
measure	O
of	O
the	O
speed	O
of	O
memory	B-General_Concept
:	O
the	O
less	O
the	O
latency	O
,	O
the	O
faster	O
the	O
reading	O
operation	O
.	O
</s>
<s>
Latency	O
should	O
not	O
be	O
confused	O
with	O
memory	B-General_Concept
bandwidth	I-General_Concept
,	O
which	O
measures	O
the	O
throughput	O
of	O
memory	B-General_Concept
.	O
</s>
<s>
Over	O
time	O
,	O
memory	B-General_Concept
latencies	I-General_Concept
expressed	O
in	O
clock	O
cycles	O
have	O
been	O
fairly	O
stable	O
,	O
but	O
they	O
have	O
improved	O
in	O
time	O
.	O
</s>
