<s>
The	O
IBM	B-Device
System/360	I-Device
Model	I-Device
67	I-Device
(	O
S/360	B-Device
-67	I-Device
)	O
was	O
an	O
important	O
IBM	B-Device
mainframe	I-Device
model	O
in	O
the	O
late	O
1960s	O
.	O
</s>
<s>
Unlike	O
the	O
rest	O
of	O
the	O
S/360	B-Application
series	O
,	O
it	O
included	O
features	O
to	O
facilitate	O
time-sharing	B-General_Concept
applications	O
,	O
notably	O
a	O
Dynamic	B-General_Concept
Address	I-General_Concept
Translation	I-General_Concept
unit	I-General_Concept
,	O
the	O
"	O
DAT	O
box	O
"	O
,	O
to	O
support	O
virtual	B-Architecture
memory	I-Architecture
,	O
32-bit	O
addressing	O
and	O
the	O
2846	O
Channel	O
Controller	O
to	O
allow	O
sharing	O
channels	O
between	O
processors	O
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
was	O
otherwise	O
compatible	O
with	O
the	O
rest	O
of	O
the	O
S/360	B-Application
series	O
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
was	O
intended	O
to	O
satisfy	O
the	O
needs	O
of	O
key	O
time-sharing	B-General_Concept
customers	O
,	O
notably	O
MIT	O
(	O
where	O
Project	O
MAC	O
had	O
become	O
a	O
notorious	O
IBM	O
sales	O
failure	O
)	O
,	O
the	O
University	O
of	O
Michigan	O
,	O
General	O
Motors	O
,	O
Bell	O
Labs	O
,	O
Princeton	O
University	O
,	O
the	O
Carnegie	O
Institute	O
of	O
Technology	O
(	O
later	O
Carnegie	O
Mellon	O
University	O
)	O
,	O
and	O
the	O
Naval	O
Postgraduate	O
School	O
.	O
</s>
<s>
In	O
the	O
mid-1960s	O
a	O
number	O
of	O
organizations	O
were	O
interested	O
in	O
offering	O
interactive	O
computing	O
services	O
using	O
time-sharing	B-General_Concept
.	O
</s>
<s>
When	O
IBM	O
introduced	O
its	O
System/360	B-Application
family	O
of	O
computers	O
in	O
the	O
mid-1960s	O
,	O
it	O
did	O
not	O
provide	O
a	O
solution	O
for	O
this	O
limitation	O
and	O
within	O
IBM	O
there	O
were	O
conflicting	O
views	O
about	O
the	O
importance	O
of	O
time-sharing	B-General_Concept
and	O
the	O
need	O
to	O
support	O
it	O
.	O
</s>
<s>
A	O
paper	O
titled	O
Program	O
and	O
Addressing	O
Structure	O
in	O
a	O
Time-Sharing	B-General_Concept
Environment	O
by	O
Bruce	O
Arden	O
,	O
Bernard	O
Galler	O
,	O
Frank	O
Westervelt	O
(	O
all	O
associate	O
directors	O
at	O
the	O
University	O
of	O
Michigan	O
's	O
academic	O
Computing	O
Center	O
)	O
,	O
and	O
Tom	O
O'Brian	O
building	O
upon	O
some	O
basic	O
ideas	O
developed	O
at	O
the	O
Massachusetts	O
Institute	O
of	O
Technology	O
(	O
MIT	O
)	O
was	O
published	O
in	O
January	O
1966	O
.	O
</s>
<s>
The	O
paper	O
outlined	O
a	O
virtual	B-Architecture
memory	I-Architecture
architecture	O
using	O
dynamic	O
address	O
translation	O
(	O
DAT	O
)	O
that	O
could	O
be	O
used	O
to	O
implement	O
time-sharing	B-General_Concept
.	O
</s>
<s>
After	O
a	O
year	O
of	O
negotiations	O
and	O
design	O
studies	O
,	O
IBM	O
agreed	O
to	O
make	O
a	O
one-of-a-kind	O
version	O
of	O
its	O
S/360	B-Application
-65	O
mainframe	O
computer	O
for	O
the	O
University	O
of	O
Michigan	O
.	O
</s>
<s>
The	O
S/360	B-Application
-65M	O
would	O
include	O
dynamic	O
address	O
translation	O
(	O
DAT	O
)	O
features	O
that	O
would	O
support	O
virtual	B-Architecture
memory	I-Architecture
and	O
allow	O
support	O
for	O
time-sharing	B-General_Concept
.	O
</s>
<s>
Initially	O
IBM	O
decided	O
not	O
to	O
supply	O
a	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
for	O
the	O
new	O
machine	O
.	O
</s>
<s>
As	O
other	O
organizations	O
heard	O
about	O
the	O
project	O
they	O
were	O
intrigued	O
by	O
the	O
time-sharing	B-General_Concept
idea	O
and	O
expressed	O
interest	O
in	O
ordering	O
the	O
modified	O
IBM	B-Application
S/360	I-Application
series	O
machines	O
.	O
</s>
<s>
With	O
this	O
demonstrated	O
interest	O
IBM	O
changed	O
the	O
computer	O
's	O
model	O
number	O
to	O
S/360	B-Device
-67	I-Device
and	O
made	O
it	O
a	O
supported	O
product	O
.	O
</s>
<s>
When	O
IBM	O
realized	O
there	O
was	O
a	O
market	O
for	O
time-sharing	B-General_Concept
,	O
it	O
agreed	O
to	O
develop	O
a	O
new	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
called	O
IBM	B-Application
Time	I-Application
Sharing	I-Application
System	I-Application
(	O
TSS/360	B-Application
)	O
for	O
delivery	O
at	O
roughly	O
the	O
same	O
time	O
as	O
the	O
first	O
model	O
S/360	B-Device
-67	I-Device
.	O
</s>
<s>
The	O
first	O
S/360	B-Device
-67	I-Device
was	O
shipped	O
in	O
May	O
1966	O
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
was	O
withdrawn	O
on	O
March	O
15	O
,	O
1977	O
.	O
</s>
<s>
IBM	O
announced	O
the	O
S/360	B-Device
-67	I-Device
in	O
its	O
August	O
16	O
,	O
1965	O
"	O
blue	O
letters	O
"	O
(	O
a	O
standard	O
mechanism	O
used	O
by	O
IBM	O
to	O
make	O
product	O
announcements	O
)	O
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
design	O
added	O
a	O
component	O
for	O
implementing	O
virtual	B-Architecture
memory	I-Architecture
,	O
the	O
"	O
DAT	O
box	O
"	O
(	O
Dynamic	O
Address	O
Translation	O
box	O
)	O
.	O
</s>
<s>
DAT	O
on	O
the	O
360/67	B-Device
was	O
based	O
on	O
the	O
architecture	O
outlined	O
in	O
a	O
1966	O
JACM	O
paper	O
by	O
Arden	O
,	O
Galler	O
,	O
Westervelt	O
,	O
and	O
O'Brien	O
and	O
included	O
both	O
segment	O
and	O
page	O
tables	O
.	O
</s>
<s>
The	O
Model	O
67	O
's	O
virtual	B-Architecture
memory	I-Architecture
support	O
was	O
very	O
similar	O
to	O
the	O
virtual	B-Architecture
memory	I-Architecture
support	O
that	O
eventually	O
became	O
standard	O
on	O
the	O
entire	O
System/370	B-Device
line	O
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
provided	O
a	O
24	O
-	O
or	O
32-bit	O
address	B-General_Concept
space	I-General_Concept
unlike	O
the	O
strictly	O
24-bit	O
address	B-General_Concept
space	I-General_Concept
of	O
other	O
S/360	B-Application
and	O
early	O
S/370	B-Device
systems	O
,	O
and	O
the	O
31-bit	O
address	B-General_Concept
space	I-General_Concept
of	O
S/370	B-Device
-XA	I-Device
available	O
on	O
later	O
S/370s	B-Device
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
virtual	O
address	B-General_Concept
space	I-General_Concept
was	O
divided	O
into	O
pages	O
(	O
of	O
4096	O
bytes	O
)	O
grouped	O
into	O
segments	O
(	O
of	O
1	O
million	O
bytes	O
)	O
;	O
pages	O
were	O
dynamically	O
mapped	O
onto	O
the	O
processor	O
's	O
real	O
memory	O
.	O
</s>
<s>
These	O
S/360	B-Device
-67	I-Device
features	O
plus	O
reference	O
and	O
change	O
bits	O
as	O
part	O
of	O
the	O
storage	O
key	O
enabled	O
operating	O
systems	O
to	O
implement	O
demand	B-General_Concept
paging	I-General_Concept
:	O
referencing	O
a	O
page	O
that	O
was	O
not	O
in	O
memory	O
caused	O
a	O
page	B-General_Concept
fault	I-General_Concept
,	O
which	O
in	O
turn	O
could	O
be	O
intercepted	O
and	O
processed	O
by	O
an	O
operating	O
system	O
interrupt	B-General_Concept
handler	I-General_Concept
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
'	O
s	O
virtual	B-Architecture
memory	I-Architecture
system	O
was	O
capable	O
of	O
meeting	O
three	O
distinct	O
goals	O
:	O
</s>
<s>
Large	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
It	O
mapped	O
physical	O
memory	O
onto	O
a	O
larger	O
pool	O
of	O
virtual	B-Architecture
memory	I-Architecture
,	O
which	O
could	O
be	O
dynamically	O
swapped	O
in	O
and	O
out	O
of	O
real	O
memory	O
as	O
needed	O
from	O
random-access	O
storage	O
(	O
typically	O
:	O
disk	O
or	O
drum	O
storage	O
)	O
.	O
</s>
<s>
Multiple	O
address	B-General_Concept
spaces	I-General_Concept
.	O
</s>
<s>
By	O
implementing	O
multiple	O
virtual	O
address	B-General_Concept
spaces	I-General_Concept
,	O
each	O
for	O
a	O
different	O
user	O
,	O
each	O
user	O
could	O
potentially	O
have	O
a	O
private	O
virtual	B-Architecture
machine	I-Architecture
.	O
</s>
<s>
The	O
third	O
enabled	O
the	O
implementation	O
of	O
true	O
virtual	B-Architecture
machines	I-Architecture
.	O
</s>
<s>
Contemporary	O
documents	O
make	O
it	O
clear	O
that	O
full	O
hardware	O
virtualization	O
and	O
virtual	B-Architecture
machines	I-Architecture
were	O
not	O
original	O
design	O
goals	O
for	O
the	O
S/360	B-Device
-67	I-Device
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
included	O
the	O
following	O
extensions	O
in	O
addition	O
to	O
the	O
standard	O
and	O
optional	O
features	O
available	O
on	O
all	O
S/360	B-Application
systems	O
:	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
operated	O
with	O
a	O
basic	O
internal	O
cycle	O
time	O
of	O
200	O
nanoseconds	O
and	O
a	O
basic	O
750	O
nanosecond	O
magnetic	O
core	O
storage	O
cycle	O
,	O
the	O
same	O
as	O
the	O
S/360	B-Application
-65	O
.	O
</s>
<s>
The	O
200	O
ns	O
cycle	O
time	O
put	O
the	O
S/360	B-Device
-67	I-Device
in	O
the	O
middle	O
of	O
the	O
S/360	B-Application
line	O
,	O
between	O
the	O
Model	O
30	O
at	O
the	O
low	O
end	O
and	O
the	O
Model	O
195	O
at	O
the	O
high	O
end	O
.	O
</s>
<s>
Four	O
new	O
components	O
were	O
part	O
of	O
the	O
S/360	B-Device
-67	I-Device
:	O
</s>
<s>
2365	B-Device
Processor	O
Storage	O
Model	O
12	O
,	O
</s>
<s>
These	O
components	O
,	O
together	O
with	O
the	O
2365	B-Device
Processor	O
Storage	O
Model	O
2	O
,	O
2860	O
Selector	O
Channel	O
,	O
2870	O
Multiplexer	O
Channel	O
,	O
and	O
other	O
System/360	B-Application
control	O
units	O
and	O
devices	O
were	O
available	O
for	O
use	O
with	O
the	O
S/360	B-Device
-67	I-Device
.	O
</s>
<s>
Note	O
that	O
while	O
Carnegie	O
Tech	O
had	O
a	O
360/67	B-Device
with	O
an	O
IBM	B-Device
2361	I-Device
LCS	O
,	O
that	O
option	O
was	O
not	O
listed	O
in	O
the	O
price	O
book	O
and	O
may	O
not	O
have	O
worked	O
in	O
a	O
duplex	O
configuration	O
.	O
</s>
<s>
Three	O
basic	O
configurations	O
were	O
available	O
for	O
the	O
IBM	B-Device
System/360	I-Device
model	I-Device
67	I-Device
:	O
</s>
<s>
When	O
the	O
S/360	B-Device
-67	I-Device
was	O
announced	O
in	O
August	O
1965	O
,	O
IBM	O
also	O
announced	O
TSS/360	B-Application
,	O
a	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
project	O
that	O
was	O
canceled	O
in	O
1971	O
(	O
having	O
also	O
been	O
canceled	O
in	O
1968	O
,	O
but	O
reprieved	O
in	O
1969	O
)	O
.	O
</s>
<s>
IBM	O
subsequently	O
modified	O
TSS/360	B-Application
and	O
offered	O
the	O
TSS/370	B-Application
PRPQ	O
for	O
three	O
releases	O
before	O
cancelling	O
it	O
.	O
</s>
<s>
MTS	B-Application
,	O
the	O
Michigan	B-Application
Terminal	I-Application
System	I-Application
,	O
was	O
the	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
developed	O
at	O
the	O
University	O
of	O
Michigan	O
and	O
first	O
used	O
on	O
the	O
Model	O
67	O
in	O
January	O
1967	O
.	O
</s>
<s>
Virtual	B-Architecture
memory	I-Architecture
support	O
was	O
added	O
to	O
MTS	B-Application
in	O
October	O
1967	O
.	O
</s>
<s>
Multi-processor	O
support	O
for	O
a	O
duplex	O
S/360	B-Device
-67	I-Device
was	O
added	O
in	O
October	O
1968	O
.	O
</s>
<s>
CP/CMS	B-Application
was	O
the	O
first	O
virtual	B-Architecture
machine	I-Architecture
operating	O
system	O
.	O
</s>
<s>
CP/CMS	B-Application
was	O
essentially	O
an	O
unsupported	O
research	O
system	O
,	O
built	O
away	O
from	O
IBM	O
's	O
mainstream	O
product	O
organizations	O
,	O
with	O
active	O
involvement	O
of	O
outside	O
researchers	O
.	O
</s>
<s>
Over	O
time	O
it	O
evolved	O
into	O
a	O
fully	O
supported	O
IBM	O
operating	O
system	O
(	O
VM/370	B-Application
and	O
today	O
's	O
z/VM	B-Application
)	O
.	O
</s>
<s>
VP/CSS	B-Application
,	O
based	O
upon	O
CP/CMS	B-Application
,	O
was	O
developed	O
by	O
National	O
CSS	O
to	O
provide	O
commercial	O
time-sharing	B-General_Concept
services	O
.	O
</s>
<s>
The	O
S/360	B-Device
-67	I-Device
had	O
an	O
important	O
legacy	O
.	O
</s>
<s>
After	O
the	O
failure	O
of	O
TSS/360	B-Application
,	O
IBM	O
was	O
surprised	O
by	O
the	O
blossoming	O
of	O
a	O
time-sharing	B-General_Concept
community	O
on	O
the	O
S/360	B-Device
-67	I-Device
platform	O
(	O
CP/CMS	B-Application
,	O
MTS	B-Application
,	O
MUSIC	B-Application
)	O
.	O
</s>
<s>
By	O
taking	O
advantage	O
of	O
IBM	O
's	O
lukewarm	O
support	O
for	O
time-sharing	B-General_Concept
,	O
and	O
by	O
sharing	O
information	O
and	O
resources	O
(	O
including	O
source	O
code	O
modifications	O
)	O
,	O
they	O
built	O
and	O
supported	O
a	O
generation	O
of	O
time-sharing	B-General_Concept
centers	O
.	O
</s>
<s>
The	O
unique	O
features	O
of	O
the	O
S/360	B-Device
-67	I-Device
were	O
initially	O
not	O
carried	O
into	O
IBM	O
's	O
next	O
product	O
series	O
,	O
the	O
System/370	B-Device
,	O
although	O
the	O
370/145	B-Device
had	O
an	O
associative	B-Data_Structure
memory	I-Data_Structure
that	O
appeared	O
more	O
useful	O
for	O
paging	O
than	O
for	O
its	O
ostensible	O
purpose	O
.	O
</s>
<s>
This	O
was	O
largely	O
fallout	O
from	O
a	O
bitter	O
and	O
highly	O
visible	O
political	O
battle	O
within	O
IBM	O
over	O
the	O
merits	O
of	O
time-sharing	B-General_Concept
versus	O
batch	B-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
Initially	O
at	O
least	O
,	O
time-sharing	B-General_Concept
lost	O
.	O
</s>
<s>
However	O
,	O
IBM	O
faced	O
increasing	O
customer	O
demand	O
for	O
time-sharing	B-General_Concept
and	O
virtual	B-Architecture
memory	I-Architecture
capabilities	O
.	O
</s>
<s>
IBM	O
also	O
could	O
not	O
ignore	O
the	O
large	O
number	O
of	O
S/360	B-Device
-67	I-Device
time-sharing	B-General_Concept
installations	O
including	O
the	O
new	O
industry	O
of	O
time-sharing	B-General_Concept
vendors	O
,	O
such	O
as	O
National	O
CSS	O
and	O
Interactive	O
Data	O
Corporation	O
(	O
IDC	O
)	O
,	O
that	O
were	O
quickly	O
achieving	O
commercial	O
success	O
.	O
</s>
<s>
In	O
1972	O
,	O
IBM	O
added	O
virtual	B-Architecture
memory	I-Architecture
features	O
to	O
the	O
S/370	B-Device
series	O
,	O
a	O
move	O
seen	O
by	O
many	O
as	O
a	O
vindication	O
of	O
work	O
done	O
on	O
the	O
S/360	B-Device
-67	I-Device
project	O
;	O
the	O
microcode	O
in	O
the	O
370/145	B-Device
was	O
updated	O
to	O
use	O
the	O
associative	B-Data_Structure
memory	I-Data_Structure
for	O
virtual	B-Architecture
address	I-Architecture
translation	I-Architecture
.	O
</s>
<s>
The	O
survival	O
and	O
success	O
of	O
IBM	O
's	O
VM	B-Application
family	O
,	O
and	O
of	O
virtualization	O
technology	O
in	O
general	O
,	O
also	O
owe	O
much	O
to	O
the	O
S/360	B-Device
-67	I-Device
.	O
</s>
<s>
In	O
2010	O
,	O
in	O
the	O
technical	O
description	O
of	O
its	O
latest	O
mainframe	O
,	O
the	O
z196	O
,	O
IBM	O
stated	O
that	O
its	O
software	O
virtualization	O
started	O
with	O
the	O
System/360	B-Device
model	I-Device
67	I-Device
.	O
</s>
