<s>
Predominantly	O
,	O
this	O
is	O
achieved	O
through	O
active-state	O
link	O
power	O
management	O
;	O
i.e.	O
,	O
the	O
PCI	O
Express	O
serial	B-Protocol
link	I-Protocol
is	O
powered	O
down	O
when	O
there	O
is	O
no	O
traffic	O
across	O
it	O
.	O
</s>
<s>
It	O
is	O
normally	O
used	O
on	O
laptops	B-Device
and	O
other	O
mobile	B-Device
Internet	I-Device
devices	I-Device
to	O
extend	O
battery	O
life	O
.	O
</s>
<s>
As	O
serial-based	B-Protocol
PCI	O
Express	O
devices	O
become	O
less	O
active	O
,	O
it	O
is	O
possible	O
for	O
the	O
computer	O
's	O
power	O
management	O
system	O
to	O
take	O
the	O
opportunity	O
to	O
reduce	O
overall	O
power	O
consumption	O
by	O
placing	O
the	O
link	O
PHY	O
into	O
a	O
low-power	O
mode	O
and	O
instructing	O
other	O
devices	O
on	O
the	O
link	O
to	O
follow	O
suit	O
.	O
</s>
<s>
This	O
is	O
usually	O
managed	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
's	O
power	O
management	O
software	O
or	O
through	O
the	O
BIOS	B-Operating_System
,	O
thus	O
different	O
settings	O
can	O
be	O
configured	O
for	O
laptop	B-Device
battery	O
mode	O
versus	O
running	O
from	O
the	O
battery	B-Application
charger	I-Application
.	O
</s>
<s>
L0s	O
concerns	O
setting	O
low	O
power	O
mode	O
for	O
one	O
direction	O
of	O
the	O
serial	B-Protocol
link	I-Protocol
only	O
,	O
usually	O
downstream	O
of	O
the	O
PHY	O
controller	O
.	O
</s>
