<s>
The	O
IBM	B-Device
9020	I-Device
was	O
an	O
IBM	B-Application
System/360	I-Application
computer	O
adapted	O
into	O
a	O
multiprocessor	O
system	O
for	O
use	O
by	O
the	O
U.S.	O
FAA	O
for	O
Air	B-Application
Traffic	I-Application
Control	I-Application
.	O
</s>
<s>
The	O
IBM	O
9020A	O
,	O
for	O
example	O
,	O
was	O
based	O
on	O
the	O
S/360	B-Device
-50	I-Device
and	O
the	O
9020D	O
used	O
two	O
out	O
of	O
three	O
or	O
four	O
S/360	B-Device
-65	I-Device
processors	O
for	O
flight	O
and	O
radar	O
data	O
processing	O
with	O
two	O
out	O
of	O
three	O
S/360	B-Device
-50	I-Device
processors	O
providing	O
input/output	O
capability	O
.	O
</s>
<s>
The	O
9020A	O
and	O
9020D	O
CCCs	O
carried	O
out	O
flight	O
and	O
radar	O
data	O
processing	O
but	O
needed	O
an	O
attached	O
display	O
complex	O
to	O
provide	O
a	O
plan	O
view	O
display	O
(	O
PVD	O
)	O
to	O
the	O
air	B-Application
traffic	I-Application
controllers	O
.	O
</s>
<s>
A	O
maximum	O
configuration	O
CCC/DCC	O
complex	O
contained	O
12	O
IBM	B-Application
S/360	I-Application
mainframes	B-Architecture
.	O
</s>
<s>
The	O
U.K.	O
centre	O
had	O
a	O
9020D	O
"	O
Triplex	O
"	O
system	O
with	O
six	O
IBM	B-Application
S/360s	I-Application
(	O
three	O
S/360	B-Application
-65s	O
and	O
three	O
S/360	B-Application
-50s	O
)	O
.	O
</s>
<s>
The	O
9020As	O
and	O
9020Ds	O
were	O
in	O
service	O
in	O
North	O
America	O
until	O
1989	O
when	O
they	O
were	O
finally	O
replaced	O
by	O
IBM	B-Device
3083	I-Device
BX1	O
mainframes	B-Architecture
as	O
part	O
of	O
the	O
FAA	O
's	O
HOST	O
Computer	O
System	O
(	O
HCS	O
)	O
upgrade	O
.	O
</s>
<s>
One	O
reason	O
for	O
the	O
1999	O
upgrade	O
was	O
concern	O
,	O
probably	O
unfounded	O
,	O
that	O
the	O
IBM	B-Device
3083	I-Device
's	O
microcode	O
would	O
not	B-Error_Name
operate	I-Error_Name
properly	I-Error_Name
in	I-Error_Name
the	I-Error_Name
year	I-Error_Name
2000	I-Error_Name
.	O
</s>
<s>
At	O
least	O
during	O
the	O
first	O
phase	O
of	O
the	O
upgrade	O
,	O
the	O
9672s	O
were	O
running	O
the	O
FAA	O
's	O
original	O
assembly	B-Language
language	I-Language
code	O
in	O
System/360	B-Application
emulation	O
mode	O
.	O
</s>
<s>
This	O
system	O
was	O
known	O
as	O
the	O
Host	O
Computer	O
System	O
(	O
HCS	O
)	O
,	O
and	O
it	O
retained	O
the	O
System/360	B-Application
technology	O
Peripheral	O
Adapter	O
Modules	O
(	O
PAMs	O
)	O
from	O
the	O
9020D	O
.	O
</s>
