<s>
The	O
IBM	O
308X	O
is	O
a	O
line	O
of	O
mainframe	B-Architecture
computers	I-Architecture
,	O
of	O
which	O
the	O
first	O
model	O
,	O
the	O
Model	O
3081	O
Processor	O
Complex	O
,	O
was	O
introduced	O
November	O
12	O
,	O
1980	O
.	O
</s>
<s>
The	O
IBM	O
308X	O
line	O
introduced	O
the	O
System/370	B-Device
Extended	O
Architecture	O
(	O
S/370	B-Device
-XA	I-Device
)	O
required	O
by	O
the	O
new	O
MVS/SP	O
V2	O
and	O
the	O
Start	O
Interpretive	O
Execution	O
(	O
SIE	O
)	O
instruction	O
used	O
by	O
the	O
new	O
Virtual	O
Machine/eXtended	O
Architecture	O
Migration	O
Aid	O
(	O
VM/XA	O
MA	O
)	O
.	O
</s>
<s>
All	O
three	O
308X	O
systems	O
,	O
which	O
IBM	O
had	O
marketed	O
as	O
"	O
System/370	B-Device
-Compatibles	O
,	O
"	O
were	O
withdrawn	O
August	O
4	O
,	O
1987	O
.	O
</s>
<s>
"	O
The	O
IBM	B-Device
3081	I-Device
Processor	O
Complex	O
offers	O
flexible	O
growth	O
steps	O
in	O
the	O
308X	O
family	O
of	O
processors	O
,	O
between	O
the	O
3083	O
Model	O
Groups	O
F	O
,	O
B	O
and	O
J	O
and	O
the	O
3084.	O
"	O
</s>
<s>
Both	O
central	O
processors	O
have	O
access	O
to	O
channels	B-Device
(	O
as	O
many	O
as	O
24	O
)	O
,	O
and	O
main	O
memory	O
(	O
up	O
to	O
32	O
megabytes	O
)	O
.	O
</s>
<s>
The	O
elimination	O
of	O
a	O
layer	O
of	O
packaging	O
was	O
achieved	O
through	O
the	O
development	O
of	O
the	O
Thermal	B-General_Concept
Conduction	I-General_Concept
Module	I-General_Concept
(	O
TCM	O
)	O
,	O
a	O
flat	O
ceramic	O
module	O
containing	O
about	O
30,000	O
logic	O
circuits	O
on	O
up	O
to	O
118	O
chips	O
.	O
</s>
<s>
The	O
TTL	B-General_Concept
chips	O
(	O
which	O
were	O
not	O
compatible	O
with	O
the	O
TTL	B-General_Concept
chips	O
sold	O
on	O
the	O
open	O
market	O
by	O
many	O
manufacturers	O
)	O
were	O
joined	O
face-down	O
(	O
sometimes	O
called	O
"	O
flip	B-Device
chip	I-Device
"	O
)	O
to	O
the	O
TCM	O
with	O
an	O
array	O
of	O
11	O
×	O
11	O
solder	O
pads	O
.	O
</s>
<s>
The	O
IBM	O
3083	O
was	O
described	O
by	O
an	O
IBMer	O
as	O
"	O
never	O
intended	O
to	O
be	O
built	O
,	O
"	O
adding	O
that	O
the	O
308X	O
was	O
to	O
only	O
be	O
the	O
3081	O
and	O
3084	O
,	O
and	O
that	O
the	O
3083	O
was	O
aimed	O
at	O
"	O
the	O
ACP/TPF	O
market	O
"	O
which	O
wanted	O
a	O
"	O
fast	O
...	O
</s>
<s>
uniprocessor.	O
"	O
</s>
