<s>
Advanced	B-Application
Comprehensive	I-Application
Operating	I-Application
System	I-Application
(	O
ACOS	O
)	O
is	O
a	O
family	O
of	O
mainframe	B-Architecture
computer	I-Architecture
operating	B-General_Concept
systems	I-General_Concept
developed	O
by	O
NEC	O
for	O
the	O
Japanese	O
market	O
.	O
</s>
<s>
It	O
consists	O
of	O
three	O
systems	O
,	O
based	O
on	O
the	O
General	B-Application
Comprehensive	I-Application
Operating	I-Application
System	I-Application
family	O
developed	O
by	O
General	O
Electric	O
,	O
Honeywell	O
,	O
and	O
Bull	O
.	O
</s>
<s>
Two	O
of	O
these	O
systems	O
,	O
ACOS-2	O
(	O
based	O
on	O
GCOS	B-Application
4	O
)	O
and	O
ACOS-4	B-Application
(	O
based	O
on	O
GCOS	B-Application
7	O
)	O
are	O
still	O
sold	O
,	O
although	O
only	O
ACOS-4	B-Application
is	O
under	O
active	O
development	O
.	O
</s>
<s>
ACOS-6	O
(	O
based	O
on	O
GCOS	B-Application
8	O
)	O
is	O
an	O
obsolete	O
high-end	O
mainframe	B-Architecture
platform	O
,	O
which	O
ceased	O
active	O
development	O
in	O
the	O
early	O
2000s	O
.	O
</s>
<s>
The	O
first	O
two	O
models	O
in	O
NEC	O
's	O
SX	B-Device
series	I-Device
of	I-Device
supercomputers	I-Device
,	O
the	O
SX-1	O
and	O
the	O
SX-2	O
(	O
released	O
in	O
1985	O
)	O
,	O
ran	O
an	O
operating	B-General_Concept
system	I-General_Concept
derived	O
from	O
ACOS-4	B-Application
,	O
which	O
was	O
variously	O
called	O
either	O
SX-OS	B-Application
or	O
SXCP	O
(	O
SX	O
System	O
Control	O
Program	O
)	O
.	O
</s>
<s>
In	O
late	O
September	O
2012	O
,	O
NEC	O
announced	O
a	O
return	O
from	O
IA-64	B-General_Concept
to	O
the	O
previous	O
NOAH	O
line	O
of	O
proprietary	B-Application
mainframe	B-Architecture
processors	O
for	O
ACOS-4	B-Application
,	O
now	O
produced	O
in	O
a	O
quad-core	O
variant	O
on	O
40	O
nm	O
,	O
called	O
NOAH-6	O
.	O
</s>
<s>
ACOS-2	O
runs	O
on	O
Intel	B-Device
Xeon	I-Device
servers	O
.	O
</s>
