<s>
The	O
Pentium	B-Device
OverDrive	I-Device
was	O
a	O
microprocessor	B-Architecture
marketing	O
brand	O
name	O
used	O
by	O
Intel	O
,	O
to	O
cover	O
a	O
variety	O
of	O
consumer	O
upgrade	O
products	O
sold	O
in	O
the	O
mid-1990s	O
.	O
</s>
<s>
It	O
was	O
originally	O
released	O
for	O
486	B-General_Concept
motherboards	O
,	O
and	O
later	O
some	O
Pentium	O
sockets	O
.	O
</s>
<s>
The	O
Pentium	B-Device
OverDrive	I-Device
is	O
a	O
heavily	O
modified	O
,	O
3.3	O
volt	O
Pentium	O
P54	O
core	O
manufactured	O
on	O
0.6	B-Algorithm
micrometer	I-Algorithm
technology	O
.	O
</s>
<s>
It	O
is	O
fitted	O
with	O
a	O
486-compatible	O
bus	B-General_Concept
unit	O
(	O
though	O
with	O
an	O
increased	O
pin-count	O
)	O
,	O
an	O
integrated	O
heatsink	O
and	O
fan	O
,	O
and	O
32	O
kB	O
of	O
level	B-General_Concept
1	I-General_Concept
cache	I-General_Concept
,	O
double	O
the	O
16	O
kB	O
offered	O
on	O
regular	O
P54C	O
chips	O
.	O
</s>
<s>
As	O
the	O
data	B-General_Concept
bus	I-General_Concept
was	O
effectively	O
reduced	O
to	O
32-bit	O
width	O
,	O
per-clock	O
performance	O
was	O
much	O
lower	O
than	O
that	O
of	O
a	O
'	O
regular	O
 '	O
Pentium	O
,	O
though	O
still	O
substantially	O
faster	O
compared	O
to	O
a	O
similarly	O
clocked	O
486	B-General_Concept
owing	O
to	O
the	O
Pentium	O
's	O
architectural	O
improvements	O
,	O
such	O
as	O
the	O
much	O
improved	O
FPU	B-General_Concept
.	O
</s>
<s>
It	O
was	O
also	O
equipped	O
with	O
an	O
integrated	O
3.3	O
volt	O
power	O
regulator	O
as	O
many	O
486	B-General_Concept
motherboards	O
only	O
provided	O
5	O
volt	O
power	O
.	O
</s>
<s>
The	O
63MHz	O
model	O
was	O
launched	O
in	O
February	O
1995	O
,	O
and	O
supported	O
25MHz	O
bus	B-General_Concept
systems	O
.	O
</s>
<s>
The	O
much	O
faster	O
83MHz	O
version	O
,	O
which	O
supported	O
both	O
25	O
(	O
63MHz	O
effective	O
)	O
and	O
33MHz	O
bus	B-General_Concept
systems	O
,	O
launched	O
much	O
later	O
the	O
same	O
year	O
on	O
September	O
,	O
and	O
was	O
very	O
expensive	O
at	O
$299	O
compared	O
to	O
other	O
upgrade	O
alternatives	O
,	O
such	O
as	O
those	O
based	O
on	O
AMD	B-Device
's	I-Device
5x86	I-Device
and	O
Cyrix	B-Device
's	I-Device
Cx5x86	I-Device
chips	O
.	O
</s>
<s>
In	O
addition	O
,	O
some	O
older	O
chipsets	O
do	O
not	O
support	O
the	O
write-back	O
functionality	O
of	O
the	O
chip	O
's	O
level	B-General_Concept
1	I-General_Concept
cache	I-General_Concept
,	O
which	O
could	O
also	O
reduce	O
performance	O
.	O
</s>
<s>
However	O
,	O
the	O
majority	O
of	O
Socket	O
3	O
motherboards	O
,	O
particularly	O
later	O
(	O
post-1994	O
)	O
VLB	O
and	O
most	O
PCI	O
boards	O
,	O
provide	O
proper	O
support	O
for	O
the	O
Pentium	B-Device
OverDrive	I-Device
including	O
fully	O
operational	O
access	O
to	O
the	O
level	O
2	O
cache	O
,	O
and	O
many	O
earlier	O
boards	O
also	O
support	O
the	O
processor	O
with	O
varying	O
levels	O
of	O
compatibility	O
and	O
performance	O
.	O
</s>
<s>
Performance-wise	O
,	O
many	O
popular	O
synthetic	O
benchmarks	O
of	O
the	O
time	O
showed	O
the	O
Pentium	B-Device
OverDrive	I-Device
under-performing	O
its	O
much	O
cheaper	O
and	O
higher-clocked	O
rivals	O
,	O
though	O
its	O
real-world	O
performance	O
(	O
given	O
the	O
motherboard	B-General_Concept
cache	I-General_Concept
was	O
being	O
optimally	O
used	O
)	O
could	O
be	O
much	O
different	O
:	O
programs	O
that	O
were	O
floating-point	O
dependent	O
or	O
optimized	O
for	O
the	O
Pentium	O
architecture	O
(	O
as	O
were	O
both	O
becoming	O
increasingly	O
common	O
in	O
the	O
mid	O
to	O
late	O
nineties	O
)	O
derived	O
a	O
more	O
substantial	O
benefit	O
from	O
the	O
Pentium	B-Device
OverDrive	I-Device
,	O
particularly	O
the	O
83MHz	O
version	O
.	O
</s>
<s>
thumb|150px|Pentium	O
Overdrive	O
for	O
Socket	B-Device
4	I-Device
,	O
120/133	O
MHz	O
.	O
</s>
<s>
thumb|150px|Pentium	O
Overdrive	O
MMX	B-Architecture
,	O
166	O
MHz	O
.	O
</s>
<s>
The	O
original	O
Socket	B-Device
4	I-Device
Pentium	O
chips	O
ran	O
at	O
higher	O
voltages	O
(	O
5V	O
)	O
than	O
later	O
models	O
.	O
</s>
<s>
The	O
OverDrive	O
Processors	O
for	O
the	O
Pentium	O
75	O
,	O
90	O
and	O
100	O
were	O
also	O
released	O
(	O
Socket	B-General_Concept
5	I-General_Concept
,	O
3.3	O
V	O
)	O
,	O
running	O
at	O
125	O
,	O
150	O
and	O
166MHz	O
(	O
clock	O
multiplier	O
of	O
2.5	O
)	O
.	O
</s>
<s>
These	O
were	O
replaced	O
by	O
Pentium	O
OverDriveMMX	O
,	O
which	O
also	O
upgraded	O
the	O
Pentium	O
120	O
-	O
200MHz	O
to	O
the	O
faster	O
version	O
with	O
MMX	B-Architecture
technology	O
.	O
</s>
<s>
In	O
1998	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
OverDrive	O
,	O
part	O
number	O
PODP66X333	O
,	O
was	O
released	O
as	O
an	O
upgrade	O
path	O
for	O
Pentium	B-Device
Pro	I-Device
owners	O
.	O
</s>
<s>
This	O
upgrade	O
could	O
be	O
used	O
in	O
single	O
and	O
dual	O
processor	O
Socket	B-Device
8	I-Device
systems	O
,	O
or	O
in	O
two	O
sockets	O
of	O
quad	O
processor	O
Socket	B-Device
8	I-Device
systems	O
with	O
CPU	O
3	O
and	O
4	O
removed	O
.	O
</s>
<s>
Combining	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
Deschutes	O
core	O
in	O
a	O
flip-chip	B-Device
package	O
with	O
a	O
512	O
kB	O
full	O
speed	O
L2	O
cache	O
chip	O
from	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
Xeon	O
into	O
a	O
Socket	O
8-compatible	O
module	O
resulted	O
in	O
a	O
300	O
or	O
333MHz	O
processor	O
that	O
could	O
run	O
on	O
a	O
60	O
or	O
66MHz	O
front	B-Architecture
side	I-Architecture
bus	I-Architecture
.	O
</s>
<s>
This	O
combination	O
brought	O
together	O
some	O
of	O
the	O
more	O
attractive	O
aspects	O
of	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
and	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
Xeon	O
:	O
MMX	B-Architecture
support/improved	O
16-bit	O
performance	O
and	O
full-speed	O
L2	O
cache	O
,	O
respectively	O
.	O
</s>
<s>
The	O
later	O
"	O
Dixon	O
"	O
mobile	B-General_Concept
Pentium	I-General_Concept
II	I-General_Concept
core	O
would	O
emulate	O
this	O
combination	O
with	O
its	O
256	O
kB	O
of	O
full-speed	O
cache	O
.	O
</s>
<s>
In	O
Intel	O
's	O
"	O
Family/Model/Stepping	O
"	O
scheme	O
,	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
OverDrive	B-Device
CPU	I-Device
is	O
family	O
6	O
,	O
model	O
3	O
.	O
</s>
<s>
Though	O
it	O
was	O
based	O
on	O
the	O
Deschutes	O
core	O
,	O
when	O
queried	O
by	O
the	O
CPUID	B-Architecture
command	O
,	O
it	O
identified	O
as	O
a	O
Klamath	O
Pentium	B-General_Concept
II	I-General_Concept
.	O
</s>
<s>
As	O
noted	O
in	O
the	O
Pentium	B-General_Concept
II	I-General_Concept
Processor	O
update	O
documentation	O
from	O
Intel	O
,	O
"	O
although	O
this	O
processor	O
has	O
a	O
CPUID	B-Architecture
of	O
163xh	O
,	O
it	O
uses	O
a	O
Pentium	B-General_Concept
II	I-General_Concept
processor	O
CPUID	B-Architecture
065xh	O
processor	O
core.	O
"	O
</s>
<s>
The	O
major	O
customer	O
for	O
the	O
production	O
of	O
these	O
chips	O
was	O
Sandia	O
National	O
Laboratories	O
's	O
ASCI	B-Device
Red	I-Device
supercomputer	O
,	O
which	O
had	O
all	O
4,510	O
CPUs	O
upgraded	O
in	O
1999	O
.	O
</s>
<s>
After	O
the	O
upgrade	O
the	O
system	O
was	O
once	O
again	O
the	O
world	O
's	O
fastest	O
on	O
the	O
TOP500	B-Operating_System
.	O
</s>
