<s>
Dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
(	O
also	O
known	O
as	O
CPU	B-General_Concept
throttling	I-General_Concept
)	O
is	O
a	O
power	O
management	O
technique	O
in	O
computer	B-General_Concept
architecture	I-General_Concept
whereby	O
the	O
frequency	O
of	O
a	O
microprocessor	O
can	O
be	O
automatically	O
adjusted	O
"	O
on	O
the	O
fly	O
"	O
depending	O
on	O
the	O
actual	O
needs	O
,	O
to	O
conserve	O
power	O
and	O
reduce	O
the	O
amount	O
of	O
heat	O
generated	O
by	O
the	O
chip	O
.	O
</s>
<s>
Dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
helps	O
preserve	O
battery	O
on	O
mobile	O
devices	O
and	O
decrease	O
cooling	O
cost	O
and	O
noise	O
on	O
quiet	O
computing	O
settings	O
,	O
or	O
can	O
be	O
useful	O
as	O
a	O
security	O
measure	O
for	O
overheated	O
systems	O
(	O
e.g.	O
</s>
<s>
after	O
poor	O
overclocking	B-Application
)	O
.	O
</s>
<s>
Dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
almost	O
always	O
appear	O
in	O
conjunction	O
with	O
dynamic	O
voltage	O
scaling	O
,	O
since	O
higher	O
frequencies	O
require	O
higher	O
supply	O
voltages	O
for	O
the	O
digital	O
circuit	O
to	O
yield	O
correct	O
results	O
.	O
</s>
<s>
The	O
combined	O
topic	O
is	O
known	O
as	O
dynamic	B-General_Concept
voltage	I-General_Concept
and	I-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
(	O
DVFS	O
)	O
.	O
</s>
<s>
Processor	O
throttling	O
is	O
also	O
known	O
as	O
"	O
automatic	O
underclocking	B-Device
"	O
.	O
</s>
<s>
Automatic	O
overclocking	B-Application
(	O
boosting	O
)	O
is	O
also	O
technically	O
a	O
form	O
of	O
dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
,	O
but	O
it	O
's	O
relatively	O
new	O
and	O
usually	O
not	O
discussed	O
with	O
throttling	O
.	O
</s>
<s>
In	O
the	O
attempt	O
to	O
control	O
the	O
leakage	O
power	O
,	O
high-k	B-Algorithm
metal-gates	I-Algorithm
and	O
power	O
gating	O
have	O
been	O
common	O
methods	O
.	O
</s>
<s>
Dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
reduces	O
the	O
number	O
of	O
instructions	O
a	O
processor	O
can	O
issue	O
in	O
a	O
given	O
amount	O
of	O
time	O
,	O
thus	O
reducing	O
performance	O
.	O
</s>
<s>
Dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
by	O
itself	O
is	O
rarely	O
worthwhile	O
as	O
a	O
way	O
to	O
conserve	O
switching	O
power	O
.	O
</s>
<s>
A	O
related-but-opposite	O
technique	O
is	O
overclocking	B-Application
,	O
whereby	O
processor	O
performance	O
is	O
increased	O
by	O
ramping	O
the	O
processor	O
's	O
(	O
dynamic	O
)	O
frequency	O
beyond	O
the	O
manufacturer	O
's	O
design	O
specifications	O
.	O
</s>
<s>
One	O
major	O
difference	O
between	O
the	O
two	O
is	O
that	O
in	O
modern	O
PC	O
systems	O
overclocking	B-Application
is	O
mostly	O
done	O
over	O
the	O
Front	B-Architecture
Side	I-Architecture
Bus	I-Architecture
(	O
mainly	O
because	O
the	O
multiplier	O
is	O
normally	O
locked	O
)	O
,	O
but	O
dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
is	O
done	O
with	O
the	O
multiplier	O
.	O
</s>
<s>
Moreover	O
,	O
overclocking	B-Application
is	O
often	O
static	O
,	O
while	O
dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
is	O
always	O
dynamic	O
.	O
</s>
<s>
Intel	O
's	O
CPU	B-General_Concept
throttling	I-General_Concept
technology	O
,	O
SpeedStep	B-Device
,	O
is	O
used	O
in	O
its	O
mobile	O
and	O
desktop	O
CPU	O
lines	O
.	O
</s>
<s>
AMD	O
employs	O
two	O
different	O
CPU	B-General_Concept
throttling	I-General_Concept
technologies	O
.	O
</s>
<s>
AMD	O
's	O
Cool'n'Quiet	B-Device
technology	O
is	O
used	O
on	O
its	O
desktop	O
and	O
server	O
processor	O
lines	O
.	O
</s>
<s>
The	O
aim	O
of	O
Cool'n'Quiet	B-Device
is	O
not	O
to	O
save	O
battery	O
life	O
,	O
as	O
it	O
is	O
not	O
used	O
in	O
AMD	O
's	O
mobile	O
processor	O
line	O
,	O
but	O
instead	O
with	O
the	O
purpose	O
of	O
producing	O
less	O
heat	O
,	O
which	O
in	O
turn	O
allows	O
the	O
system	O
fan	O
to	O
spin	O
down	O
to	O
slower	O
speeds	O
,	O
resulting	O
in	O
cooler	O
and	O
quieter	O
operation	O
,	O
hence	O
the	O
name	O
of	O
the	O
technology	O
.	O
</s>
<s>
AMD	O
's	O
PowerNow	B-Device
!	I-Device
</s>
<s>
CPU	B-General_Concept
throttling	I-General_Concept
technology	O
is	O
used	O
in	O
its	O
mobile	O
processor	O
line	O
,	O
though	O
some	O
supporting	O
CPUs	O
like	O
the	O
AMD	O
K6-2	O
+	O
can	O
be	O
found	O
in	O
desktops	O
as	O
well	O
.	O
</s>
<s>
AMD	O
PowerTune	O
and	O
AMD	O
ZeroCore	O
Power	O
are	O
dynamic	B-General_Concept
frequency	I-General_Concept
scaling	I-General_Concept
technologies	O
for	O
GPUs	B-Architecture
.	O
</s>
<s>
VIA	O
Technologies	O
processors	O
use	O
a	O
technology	O
named	O
LongHaul	B-Device
(	O
PowerSaver	B-Device
)	O
,	O
while	O
Transmeta	O
's	O
version	O
was	O
called	O
LongRun	B-Device
.	O
</s>
<s>
The	O
36-processor	O
AsAP	B-General_Concept
1	I-General_Concept
chip	O
is	O
among	O
the	O
first	O
multi-core	O
processor	O
chips	O
to	O
support	O
completely	O
unconstrained	O
clock	O
operation	O
(	O
requiring	O
only	O
that	O
frequencies	O
are	O
below	O
the	O
maximum	O
allowed	O
)	O
including	O
arbitrary	O
changes	O
in	O
frequency	O
,	O
starts	O
,	O
and	O
stops	O
.	O
</s>
<s>
The	O
167-processor	O
AsAP	B-General_Concept
2	I-General_Concept
chip	O
is	O
the	O
first	O
multi-core	O
processor	O
chip	O
which	O
enables	O
individual	O
processors	O
to	O
make	O
fully	O
unconstrained	O
changes	O
to	O
their	O
own	O
clock	O
frequencies	O
.	O
</s>
<s>
According	O
to	O
the	O
ACPI	B-Device
Specs	O
,	O
the	O
C0	O
working	O
state	O
of	O
a	O
modern-day	O
CPU	O
can	O
be	O
divided	O
into	O
the	O
so-called	O
"	O
P	O
"	O
-states	O
(	O
performance	O
states	O
)	O
which	O
allow	O
clock	O
rate	O
reduction	O
and	O
"	O
T	O
"	O
-states	O
(	O
throttling	O
states	O
)	O
which	O
will	O
further	O
throttle	O
down	O
a	O
CPU	O
(	O
but	O
not	O
the	O
actual	O
clock	O
rate	O
)	O
by	O
inserting	O
STPCLK	O
(	O
stop	O
clock	O
)	O
signals	O
and	O
thus	O
omitting	O
duty	O
cycles	O
.	O
</s>
<s>
Different	O
ARM-based	O
systems	O
on	O
chip	O
provide	O
CPU	O
and	O
GPU	B-Architecture
throttling	O
.	O
</s>
