<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
,	O
also	O
known	O
by	O
its	O
code	O
name	O
,	O
EV5	O
,	O
is	O
a	O
microprocessor	B-Architecture
developed	O
and	O
fabricated	B-Architecture
by	O
Digital	O
Equipment	O
Corporation	O
that	O
implemented	O
the	O
Alpha	B-Device
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
.	O
</s>
<s>
It	O
was	O
introduced	O
in	O
January	O
1995	O
,	O
succeeding	O
the	O
Alpha	B-General_Concept
21064A	I-General_Concept
as	O
Digital	O
's	O
flagship	O
microprocessor	B-Architecture
.	O
</s>
<s>
It	O
was	O
succeeded	O
by	O
the	O
Alpha	B-General_Concept
21264	I-General_Concept
in	O
1998	O
.	O
</s>
<s>
First	O
silicon	O
of	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
was	O
produced	O
in	O
February	O
1994	O
,	O
and	O
the	O
OpenVMS	B-Operating_System
,	O
Digital	B-Operating_System
UNIX	I-Operating_System
and	O
Windows	B-Device
NT	I-Device
operating	B-General_Concept
systems	I-General_Concept
were	O
successfully	O
booted	O
on	O
it	O
.	O
</s>
<s>
The	O
final	O
Alpha	B-General_Concept
21164	I-General_Concept
,	O
a	O
333MHz	O
version	O
,	O
was	O
announced	O
on	O
2	O
October	O
1995	O
,	O
available	O
in	O
sample	O
quantities	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
was	O
replaced	O
by	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
as	O
Digital	O
's	O
flagship	O
microprocessor	B-Architecture
in	O
1996	O
when	O
a	O
400MHz	O
version	O
became	O
available	O
in	O
volume	O
quantities	O
.	O
</s>
<s>
Digital	O
used	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
operating	O
at	O
various	O
clock	O
frequencies	O
in	O
their	O
AlphaServer	B-Device
servers	B-Application
,	O
AlphaStation	B-Device
workstations	B-Device
.	O
</s>
<s>
Digital	O
also	O
used	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
in	O
their	O
Alpha	B-Device
VME	O
5/352	O
and	O
Alpha	B-Device
VME	O
5/480	O
single	B-Device
board	I-Device
computers	I-Device
and	O
AlphaPC	O
164	O
and	O
AlphaPC	O
164LX	O
motherboards	B-Device
.	O
</s>
<s>
Alpha	B-Device
partner	O
Cray	O
Research	O
used	O
a	O
300MHz	O
Alpha	B-General_Concept
21164	I-General_Concept
in	O
their	O
T3E-600	B-Device
supercomputer	O
.	O
</s>
<s>
Third	O
parties	O
such	O
as	O
DeskStation	O
also	O
built	O
workstations	B-Device
using	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
.	O
</s>
<s>
The	O
21164	O
continued	O
the	O
performance	O
lead	O
from	O
the	O
275MHz	O
Alpha	B-General_Concept
21064A	I-General_Concept
until	O
the	O
introduction	O
of	O
the	O
Intel	B-Device
Pentium	I-Device
Pro	I-Device
in	O
November	O
1995	O
,	O
when	O
a	O
200MHz	O
version	O
outperformed	O
the	O
300MHz	O
21164	O
on	O
the	O
SPECint95_base	O
benchmark	O
suite	O
.	O
</s>
<s>
The	O
21164	O
retained	O
its	O
floating-point	B-Algorithm
performance	O
lead	O
.	O
</s>
<s>
The	O
333MHz	O
21164	O
introduce	O
the	O
following	O
year	O
outperformed	O
the	O
Pentium	B-Device
Pro	I-Device
,	O
but	O
it	O
was	O
later	O
surpassed	O
by	O
the	O
MIPS	O
Technologies	O
R10000	B-General_Concept
and	O
then	O
by	O
the	O
Hewlett-Packard	O
PA-8000	B-General_Concept
in	O
the	O
same	O
year	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
is	O
a	O
four-issue	O
superscalar	B-General_Concept
microprocessor	B-Architecture
capable	O
of	O
issuing	O
a	O
maximum	O
of	O
four	O
instructions	O
per	O
clock	O
cycle	O
to	O
four	O
execution	O
units	O
:	O
two	O
integer	O
and	O
two	O
floating-point	B-Algorithm
.	O
</s>
<s>
The	O
integer	O
pipeline	O
is	O
seven	O
stages	O
long	O
,	O
and	O
the	O
floating-point	B-Algorithm
pipeline	O
is	O
ten	O
stages	O
long	O
.	O
</s>
<s>
The	O
21164	O
implemented	O
a	O
43-bit	O
virtual	B-General_Concept
address	I-General_Concept
and	O
a	O
40-bit	O
physical	B-General_Concept
address	I-General_Concept
.	O
</s>
<s>
It	O
was	O
therefore	O
capable	O
of	O
addressing	O
8TB	O
of	O
virtual	B-Architecture
memory	I-Architecture
and	O
1TB	O
of	O
physical	O
memory	B-General_Concept
.	O
</s>
<s>
The	O
integer	O
unit	O
consisted	O
of	O
two	O
integer	O
pipelines	O
and	O
the	O
integer	O
register	B-General_Concept
file	I-General_Concept
.	O
</s>
<s>
The	O
integer	O
register	B-General_Concept
file	I-General_Concept
contained	O
forty	O
64-bit	O
registers	O
,	O
of	O
which	O
thirty-two	O
are	O
specified	O
by	O
the	O
Alpha	B-Device
Architecture	O
and	O
eight	O
are	O
for	O
use	O
by	O
PALcode	B-General_Concept
as	O
scratchpad	O
memory	B-General_Concept
.	O
</s>
<s>
The	O
register	B-General_Concept
file	I-General_Concept
has	O
four	O
read	O
ports	O
and	O
two	O
write	O
ports	O
evenly	O
divided	O
between	O
the	O
two	O
integer	O
pipelines	O
.	O
</s>
<s>
The	O
floating-point	B-Algorithm
unit	O
consisted	O
of	O
two	O
floating-point	B-Algorithm
pipelines	O
and	O
the	O
floating	B-Algorithm
point	I-Algorithm
register	B-General_Concept
file	I-General_Concept
.	O
</s>
<s>
The	O
two	O
pipelines	O
are	O
not	O
identical	O
,	O
one	O
executed	O
all	O
floating-point	B-Algorithm
instructions	O
except	O
for	O
multiply	O
,	O
and	O
the	O
other	O
executed	O
only	O
multiply	O
instructions	O
.	O
</s>
<s>
A	O
non-pipelined	O
floating-point	B-Algorithm
divider	O
is	O
connected	O
to	O
the	O
add	O
pipeline	O
.	O
</s>
<s>
All	O
floating-point	B-Algorithm
instructions	O
except	O
for	O
divide	O
have	O
four-cycle	O
latency	O
.	O
</s>
<s>
Divides	O
have	O
variable	O
latency	O
that	O
depends	O
on	O
whether	O
the	O
operation	O
is	O
being	O
performed	O
on	O
single	O
or	O
on	O
double	O
precision	O
floating-point	B-Algorithm
numbers	I-Algorithm
and	O
numbers	O
.	O
</s>
<s>
The	O
21164	O
has	O
three	O
levels	O
of	O
cache	B-General_Concept
,	O
two	O
on-die	O
and	O
one	O
external	O
and	O
optional	O
.	O
</s>
<s>
The	O
primary	O
cache	B-General_Concept
is	O
split	O
into	O
separate	O
caches	O
for	O
instructions	O
and	O
data	O
,	O
referred	O
to	O
as	O
the	O
I-cache	O
and	O
D-cache	O
respectively	O
.	O
</s>
<s>
They	O
are	O
8KB	O
in	O
size	O
,	O
direct-mapped	O
and	O
have	O
a	O
cache	B-General_Concept
line	O
size	O
of	O
32	O
bytes	O
.	O
</s>
<s>
The	O
D-cache	O
is	O
dual-ported	O
,	O
to	O
improve	O
performance	O
,	O
and	O
is	O
implemented	O
by	O
duplicating	O
the	O
cache	B-General_Concept
twice	O
.	O
</s>
<s>
The	O
secondary	B-General_Concept
cache	I-General_Concept
,	O
known	O
as	O
the	O
S-cache	O
,	O
is	O
on-die	O
and	O
has	O
a	O
capacity	O
of	O
96KB	O
.	O
</s>
<s>
An	O
on-die	O
secondary	B-General_Concept
cache	I-General_Concept
was	O
required	O
as	O
the	O
21164	O
required	O
more	O
bandwidth	O
than	O
an	O
external	O
secondary	B-General_Concept
cache	I-General_Concept
could	O
supply	O
in	O
order	O
to	O
provide	O
it	O
with	O
enough	O
instructions	O
and	O
data	O
.	O
</s>
<s>
The	O
cache	B-General_Concept
required	O
two	O
cycles	O
to	O
access	O
due	O
to	O
its	O
large	O
area	O
.	O
</s>
<s>
To	O
improve	O
performance	O
,	O
the	O
cache	B-General_Concept
is	O
pipelined	O
.	O
</s>
<s>
Another	O
benefit	O
of	O
an	O
on-die	O
secondary	B-General_Concept
cache	I-General_Concept
was	O
that	O
it	O
could	O
be	O
easily	O
implemented	O
as	O
a	O
multi-way	O
cache	B-General_Concept
,	O
and	O
as	O
a	O
result	O
,	O
the	O
cache	B-General_Concept
is	O
three-way	O
set	O
associative	O
,	O
offering	O
improved	O
hit	O
rates	O
than	O
direct-mapped	O
caches	O
.	O
</s>
<s>
The	O
S-cache	O
,	O
due	O
to	O
the	O
large	O
physical	O
area	O
required	O
,	O
was	O
implemented	O
in	O
two	O
halves	O
which	O
flank	O
the	O
I-box	O
,	O
E-box	O
,	O
F-box	O
and	O
M-box	O
.	O
</s>
<s>
This	O
was	O
done	O
so	O
the	O
cache	B-General_Concept
could	O
return	O
data	O
in	O
two	O
cycles	O
.	O
</s>
<s>
The	O
tertiary	O
cache	B-General_Concept
,	O
known	O
as	O
the	O
B-cache	O
,	O
is	O
implemented	O
with	O
external	O
SRAMs	O
.	O
</s>
<s>
The	O
B-cache	O
was	O
optional	O
and	O
some	O
systems	O
using	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
did	O
not	O
have	O
any	O
.	O
</s>
<s>
The	O
B-cache	O
could	O
have	O
a	O
capacity	O
of	O
1	O
to	O
64MB	O
,	O
smaller	O
capacities	O
were	O
not	O
supported	O
as	O
they	O
were	O
rendered	O
useless	O
by	O
the	O
on-die	O
S-cache	O
.	O
</s>
<s>
The	O
B-cache	O
is	O
controlled	O
by	O
on-die	O
external	O
interface	O
logic	O
,	O
unlike	O
the	O
21064	O
,	O
which	O
required	O
an	O
external	O
cache	B-General_Concept
controller	O
.	O
</s>
<s>
The	O
B-cache	O
could	O
be	O
built	O
with	O
asynchronous	O
or	O
synchronous	O
SRAMs	O
.	O
</s>
<s>
The	O
B-cache	O
is	O
accessed	O
via	O
the	O
system	O
bus	O
.	O
</s>
<s>
The	O
system	O
bus	O
 '	O
clock	O
signal	O
is	O
generated	O
by	O
the	O
microprocessor	B-Architecture
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
therefore	O
requires	O
an	O
external	O
clock	O
signal	O
of	O
600MHz	O
for	O
a	O
300MHz	O
Alpha	B-General_Concept
21164	I-General_Concept
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
contains	O
9.3	O
million	O
transistors	O
on	O
a	O
die	O
measuring	O
16.5	O
by	O
18.1mm	O
(	O
299mm2	O
)	O
,	O
which	O
was	O
close	O
to	O
the	O
maximum	O
limits	O
of	O
the	O
process	O
.	O
</s>
<s>
The	O
die	O
was	O
fabricated	B-Architecture
in	O
Digital	O
's	O
fifth-generation	O
complementary	O
metal	O
–	O
oxide	O
–	O
semiconductor	O
(	O
CMOS	B-Device
)	O
process	O
,	O
CMOS-5	O
,	O
a	O
0.50μm	O
process	O
with	O
four	O
levels	O
of	O
aluminium	O
interconnect	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
is	O
packaged	O
in	O
a	O
499-pin	O
ceramic	O
interstitial	O
pin	B-Algorithm
grid	I-Algorithm
array	I-Algorithm
(	O
IPGA	O
)	O
measuring	O
57.40	O
by	O
57.40mm	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164	I-General_Concept
was	O
the	O
basis	O
of	O
a	O
further	O
development	O
code-named	O
EV56	B-General_Concept
.	O
</s>
<s>
It	O
was	O
introduced	O
as	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
,	O
but	O
was	O
originally	O
known	O
as	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
.	O
</s>
<s>
It	O
was	O
first	O
described	O
in	O
October	O
1995	O
at	O
the	O
Microprocessor	B-Architecture
Forum	O
.	O
</s>
<s>
Samsung	O
Electronics	O
signed	O
a	O
deal	O
with	O
Digital	O
in	O
June	O
1996	O
to	O
second	O
source	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
and	O
the	O
company	O
was	O
the	O
only	O
one	O
to	O
fabricate	O
the	O
666MHz	O
model	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164A	I-General_Concept
was	O
fabricated	B-Architecture
at	O
Digital	O
's	O
Hudson	O
,	O
Massachusetts	O
and	O
Samsung	O
's	O
Kihueng	O
,	O
South	O
Korea	O
fabrication	B-Algorithm
plants	I-Algorithm
.	O
</s>
<s>
Users	O
of	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
included	O
Cray	O
Research	O
,	O
Digital	O
,	O
Network	O
Appliance	O
(	O
now	O
NetApp	O
)	O
,	O
and	O
DeskStation	O
.	O
</s>
<s>
Cray	O
Research	O
used	O
450	O
,	O
600	O
and	O
675MHz	O
Alpha	B-General_Concept
21164As	I-General_Concept
in	O
later	O
models	O
of	O
their	O
T3E	B-Device
supercomputer	O
.	O
</s>
<s>
Digital	O
used	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
operating	O
at	O
various	O
clock	O
frequencies	O
in	O
their	O
AlphaServers	B-Device
,	O
AlphaStations	B-Device
,	O
Celebris	O
XL	O
workstations	B-Device
and	O
Digital	B-Device
Personal	I-Device
Workstations	I-Device
.	O
</s>
<s>
NetApp	O
used	O
400	O
,	O
500	O
and	O
600MHz	O
Alpha	B-General_Concept
21164As	I-General_Concept
in	O
their	O
storage	B-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
DeskStation	O
used	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
in	O
their	O
Raptor	O
Reflex	O
workstations	B-Device
.	O
</s>
<s>
The	O
most	O
notable	O
change	O
was	O
the	O
inclusion	O
of	O
Byte	O
Word	O
Extensions	O
(	O
BWX	O
)	O
,	O
an	O
extension	O
to	O
the	O
Alpha	B-Device
Architecture	O
designed	O
to	O
improve	O
byte	O
and	O
word	O
accesses	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164A	I-General_Concept
contained	O
9.66	O
million	O
transistors	O
on	O
a	O
die	O
measuring	O
14.4mm	O
by	O
14.5mm	O
,	O
for	O
a	O
die	O
area	O
of	O
209mm2	O
.	O
</s>
<s>
Digital	O
fabricated	B-Architecture
the	O
die	O
in	O
their	O
sixth	O
generation	O
CMOS	B-Device
process	O
,	O
CMOS-6	O
,	O
a	O
0.35μm	O
process	O
with	O
four	O
layers	O
of	O
interconnect	O
.	O
</s>
<s>
Samsung	O
fabricated	B-Architecture
the	O
die	O
in	O
their	O
0.35μm	O
process	O
with	O
four	O
layers	O
of	O
interconnect	O
based	O
on	O
a	O
0.3μm	O
process	O
they	O
developed	O
in	O
early	O
1996	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164A	I-General_Concept
used	O
a	O
3.3	O
V	O
power	O
supply	O
,	O
dissipating	O
31.0	O
W	O
at	O
366MHz	O
,	O
36.0	O
W	O
at	O
433MHz	O
,	O
41.0	O
W	O
at	O
500MHz	O
,	O
43.5	O
W	O
at	O
533MHz	O
and	O
48.5	O
W	O
at	O
600MHz	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164PC	I-General_Concept
,	O
also	O
known	O
as	O
the	O
PCA56	B-General_Concept
,	O
is	O
a	O
low-cost	O
version	O
of	O
the	O
Alpha	B-General_Concept
21164A	I-General_Concept
introduced	O
on	O
17	O
March	O
1997	O
.	O
</s>
<s>
The	O
microprocessor	B-Architecture
was	O
jointly	O
developed	O
by	O
Digital	O
and	O
Mitsubishi	O
Electric	O
Corporation	O
,	O
and	O
both	O
companies	O
fabricated	B-Architecture
the	O
design	O
.	O
</s>
<s>
Mitsubishi	O
later	O
suspended	O
the	O
joint	O
development	O
agreement	O
for	O
future	O
Alpha	B-Device
microprocessors	B-Architecture
with	O
Digital	O
in	O
early	O
1998	O
and	O
ceased	O
to	O
fabricate	O
the	O
Alpha	B-General_Concept
21164PC	I-General_Concept
in	O
mid-1998	O
,	O
exited	O
the	O
Alpha	B-Device
market	O
because	O
the	O
economic	O
conditions	O
in	O
the	O
company	O
's	O
markets	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164PC	I-General_Concept
operated	O
at	O
clock	O
frequencies	O
of	O
400	O
,	O
466	O
and	O
533MHz	O
.	O
</s>
<s>
Major	O
changes	O
are	O
the	O
omission	O
of	O
the	O
S-cache	O
,	O
a	O
larger	O
I-cache	O
,	O
and	O
the	O
inclusion	O
of	O
Motion	B-Device
Video	I-Device
Instructions	I-Device
(	O
MVI	O
)	O
,	O
an	O
extension	O
to	O
the	O
Alpha	B-Device
Architecture	O
which	O
introduced	O
single	B-Device
instruction	I-Device
multiple	I-Device
data	I-Device
(	O
SIMD	B-Device
)	O
instructions	O
for	O
improving	O
the	O
performance	O
of	O
MPEG	O
encoding	O
.	O
</s>
<s>
The	O
S-cache	O
was	O
removed	O
to	O
reduce	O
the	O
transistor	O
count	O
,	O
which	O
reduced	O
the	O
die	O
size	O
and	O
in	O
turn	O
,	O
cost	O
.	O
</s>
<s>
The	O
I-cache	O
was	O
doubled	O
in	O
capacity	O
to	O
16	O
KB	O
from	O
8	O
KB	O
to	O
compensate	O
for	O
the	O
lack	O
of	O
S-cache	O
,	O
as	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
relied	O
on	O
the	O
S-cache	O
to	O
complement	O
the	O
I-cache	O
in	O
order	O
to	O
provide	O
enough	O
bandwidth	O
to	O
achieve	O
adequate	O
performance	O
.	O
</s>
<s>
The	O
amount	O
of	O
B-cache	O
was	O
limited	O
to	O
512	O
KB	O
to	O
4	O
MB	O
,	O
with	O
1	O
and	O
2	O
MB	O
capacities	O
also	O
supported	O
.	O
</s>
<s>
The	O
microprocessor	B-Architecture
uses	O
a	O
43-bit	O
virtual	B-General_Concept
address	I-General_Concept
and	O
33-bit	O
physical	B-General_Concept
address	I-General_Concept
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164PC	I-General_Concept
contained	O
3.5	O
million	O
transistors	O
on	O
a	O
die	O
measuring	O
8.65	O
by	O
16.28mm	O
,	O
for	O
a	O
die	O
area	O
of	O
141mm2	O
.	O
</s>
<s>
Digital	O
fabricated	B-Architecture
the	O
die	O
in	O
the	O
same	O
process	O
as	O
the	O
Alpha	B-General_Concept
21164	I-General_Concept
,	O
CMOS-5	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164PC	I-General_Concept
was	O
packaged	O
in	O
413-pin	O
IPGA	O
measuring	O
49.78	O
by	O
49.78mm	O
.	O
</s>
<s>
The	O
Alpha	B-General_Concept
21164PC	I-General_Concept
was	O
used	O
by	O
Digital	O
in	O
their	O
AlphaPC	O
164SX	O
motherboard	B-Device
.	O
</s>
<s>
A	O
derivative	O
of	O
the	O
PCA56	B-General_Concept
,	O
the	O
PCA57	B-General_Concept
was	O
designed	O
and	O
fabricated	B-Architecture
by	O
Samsung	O
Electronics	O
in	O
a	O
0.28μm	O
CMOS	B-Device
process	O
.	O
</s>
<s>
The	O
PCA57	B-General_Concept
was	O
introduced	O
in	O
late	O
1998	O
and	O
operated	O
at	O
clock	O
frequencies	O
of	O
533	O
,	O
600	O
and	O
666MHz	O
.	O
</s>
<s>
Improvements	O
to	O
the	O
PCA56	B-General_Concept
microarchitecture	O
included	O
doubled	O
I-cache	O
and	O
D-cache	O
capacities	O
:	O
32KB	O
and	O
16KB	O
respectively	O
.	O
</s>
<s>
The	O
PCA57	B-General_Concept
contained	O
5.7	O
million	O
transistors	O
on	O
a	O
die	O
measuring	O
6.7mm	O
by	O
15mm	O
,	O
for	O
a	O
die	O
area	O
of	O
101mm2	O
.	O
</s>
<s>
The	O
PCA57	B-General_Concept
was	O
used	O
by	O
Digital	O
in	O
its	O
AlphaPC	O
164RX	O
motherboard	B-Device
.	O
</s>
<s>
Digital	O
also	O
developed	O
custom	O
application-specific	O
integrated	O
circuit	O
(	O
ASICs	O
)	O
for	O
use	O
in	O
the	O
high-end	O
models	O
of	O
their	O
AlphaServer	B-Device
family	O
such	O
as	O
the	O
AlphaServer	B-Device
8200	O
and	O
8400	O
.	O
</s>
<s>
The	O
21171	O
,	O
also	O
known	O
as	O
Alcor	O
,	O
was	O
the	O
first	O
chipset	O
for	O
the	O
21164	O
,	O
introduced	O
in	O
January	O
1995	O
alongside	O
the	O
microprocessor	B-Architecture
it	O
supports	O
.	O
</s>
<s>
It	O
was	O
developed	O
and	O
fabricated	B-Architecture
by	O
Digital	O
.	O
</s>
<s>
It	O
consisted	O
of	O
a	O
control	O
chip	O
that	O
contained	O
the	O
memory	B-General_Concept
and	O
PCI	B-Protocol
controllers	O
,	O
and	O
four	O
data	O
slice	O
chips	O
that	O
interfaced	O
the	O
256-bit	O
memory	B-General_Concept
bus	O
and	O
PCI	B-Protocol
bus	I-Protocol
to	O
the	O
system	O
bus	O
.	O
</s>
<s>
The	O
21171	O
provides	O
a	O
64-bit	O
wide	O
PCI	B-Protocol
bus	I-Protocol
that	O
runs	O
at	O
33MHz	O
.	O
</s>
<s>
The	O
Pyxis	O
chipset	O
,	O
also	O
known	O
as	O
the	O
21174	O
,	O
supported	O
the	O
21164A	O
and	O
21164PC	O
microprocessors	B-Architecture
.	O
</s>
<s>
As	O
a	O
result	O
,	O
it	O
was	O
a	O
single-chip	O
design	O
packaged	O
in	O
a	O
474-contact	O
ceramic	B-Algorithm
ball	I-Algorithm
grid	I-Algorithm
array	I-Algorithm
(	O
CBGA	O
)	O
instead	O
of	O
multiple	O
packages	O
.	O
</s>
<s>
It	O
was	O
subsequently	O
used	O
in	O
cost-sensitive	O
applications	O
such	O
as	O
entry-level	O
workstations	B-Device
(	O
Digital	B-Device
Personal	I-Device
Workstation	I-Device
a-Series	I-Device
)	O
and	O
motherboards	B-Device
such	O
as	O
the	O
AlphaPC	O
164LX	O
and	O
164SX	O
.	O
</s>
<s>
The	O
21174	O
contains	O
a	O
memory	B-General_Concept
controller	I-General_Concept
and	O
PCI	B-Protocol
controller	O
.	O
</s>
<s>
The	O
memory	B-General_Concept
controller	I-General_Concept
supported	O
up	O
to	O
512	O
MB	O
of	O
synchronous	O
dynamic	O
random	O
access	O
memory	B-General_Concept
(	O
SDRAM	O
)	O
and	O
accesses	O
it	O
via	O
a	O
128-bit	O
memory	B-General_Concept
bus	O
.	O
</s>
<s>
The	O
memory	B-General_Concept
can	O
be	O
either	O
ECC	O
or	O
parity	O
protected	O
.	O
</s>
<s>
The	O
PCI	B-Protocol
controller	O
provided	O
a	O
PCI	B-Protocol
or	O
PCI-X	O
bus	O
.	O
</s>
<s>
Polaris	O
is	O
a	O
system	O
controller	O
developed	O
by	O
VLSI	O
Technology	O
for	O
personal	O
computers	O
that	O
supports	O
the	O
21164A	O
and	O
21164PC	O
microprocessors	B-Architecture
.	O
</s>
<s>
The	O
memory	B-General_Concept
is	O
accessed	O
via	O
a	O
128-bit	O
bus	O
.	O
</s>
<s>
It	O
provides	O
a	O
32-bit	O
,	O
33MHz	O
PCI	B-Protocol
bus	I-Protocol
for	O
I/O	O
.	O
</s>
<s>
Users	O
of	O
Polaris	O
included	O
Digital	O
,	O
for	O
its	O
AlphaPC	O
164RX	O
motherboard	B-Device
.	O
</s>
