<s>
The	O
IBM	B-Application
System/360	I-Application
(	O
S/360	B-Application
)	O
is	O
a	O
family	O
of	O
mainframe	B-Architecture
computer	I-Architecture
systems	O
that	O
was	O
announced	O
by	O
IBM	O
on	O
April	O
7	O
,	O
1964	O
,	O
and	O
delivered	O
between	O
1965	O
and	O
1978	O
.	O
</s>
<s>
The	O
design	O
distinguished	O
between	O
architecture	B-General_Concept
and	O
implementation	O
,	O
allowing	O
IBM	O
to	O
release	O
a	O
suite	O
of	O
compatible	O
designs	O
at	O
different	O
prices	O
.	O
</s>
<s>
All	O
but	O
the	O
only	O
partially	O
compatible	O
Model	B-Device
44	I-Device
and	O
the	O
most	O
expensive	O
systems	O
use	O
microcode	B-Device
to	O
implement	O
the	O
instruction	B-General_Concept
set	I-General_Concept
,	O
which	O
features	O
8-bit	O
byte	B-Application
addressing	O
and	O
binary	O
,	O
decimal	O
,	O
and	O
hexadecimal	B-Device
floating-point	B-Algorithm
calculations	O
.	O
</s>
<s>
The	O
System/360	B-Application
family	O
introduced	O
IBM	O
's	O
Solid	B-Algorithm
Logic	I-Algorithm
Technology	I-Algorithm
(	O
SLT	O
)	O
,	O
which	O
packed	O
more	O
transistors	B-Application
onto	O
a	O
circuit	O
card	O
,	O
allowing	O
more	O
powerful	O
but	O
smaller	O
computers	O
to	O
be	O
built	O
.	O
</s>
<s>
The	O
slowest	O
System/360	B-Application
model	O
announced	O
in	O
1964	O
,	O
the	O
Model	B-Device
30	I-Device
,	O
could	O
perform	O
up	O
to	O
34,500	O
instructions	O
per	O
second	O
,	O
with	O
memory	O
from	O
8	O
to	O
64KB	O
.	O
</s>
<s>
The	O
1967	O
IBM	B-Device
System/360	I-Device
Model	I-Device
91	I-Device
could	O
execute	O
up	O
to	O
16.6	O
million	O
instructions	O
per	O
second	O
.	O
</s>
<s>
Up	O
to	O
8	O
megabytes	O
of	O
slower	O
(	O
8	O
microsecond	O
)	O
Large	O
Capacity	O
Storage	O
(	O
LCS	B-Device
)	O
was	O
also	O
available	O
for	O
some	O
models	O
.	O
</s>
<s>
The	O
IBM	B-Application
360	I-Application
was	O
extremely	O
successful	O
in	O
the	O
market	O
,	O
allowing	O
customers	O
to	O
purchase	O
a	O
smaller	O
system	O
with	O
the	O
knowledge	O
they	O
would	O
be	O
able	O
to	O
move	O
to	O
larger	O
ones	O
if	O
their	O
needs	O
grew	O
,	O
without	O
reprogramming	O
application	O
software	O
or	O
replacing	O
peripheral	O
devices	O
.	O
</s>
<s>
Its	O
design	O
influenced	O
computer	B-General_Concept
design	I-General_Concept
for	O
years	O
to	O
come	O
;	O
many	O
consider	O
it	O
one	O
of	O
the	O
most	O
successful	O
computers	O
in	O
history	O
.	O
</s>
<s>
The	O
chief	O
architect	O
of	O
System/360	B-Application
was	O
Gene	O
Amdahl	O
,	O
and	O
the	O
project	O
was	O
managed	O
by	O
Fred	O
Brooks	O
,	O
responsible	O
to	O
Chairman	O
Thomas	O
J	O
.	O
Watson	O
Jr.	O
</s>
<s>
The	O
commercial	O
release	O
was	O
piloted	O
by	O
another	O
of	O
Watson	O
's	O
lieutenants	O
,	O
John	O
R	O
.	O
Opel	O
,	O
who	O
managed	O
the	O
launch	O
of	O
IBM	O
’s	O
System	B-Application
360	I-Application
mainframe	B-Architecture
family	O
in	O
1964	O
.	O
</s>
<s>
Application-level	O
compatibility	O
(	O
with	O
some	O
restrictions	O
)	O
for	O
System/360	B-Application
software	O
is	O
maintained	O
to	O
the	O
present	O
day	O
with	O
the	O
System	B-Device
z	I-Device
mainframe	B-Architecture
servers	I-Architecture
.	O
</s>
<s>
Contrasting	O
with	O
industry	O
practice	O
of	O
the	O
day	O
,	O
IBM	O
created	O
an	O
entire	O
new	O
series	O
of	O
computers	O
,	O
from	O
small	O
to	O
large	O
,	O
low	O
-	O
to	O
high-performance	O
,	O
all	O
using	O
the	O
same	O
instruction	B-General_Concept
set	I-General_Concept
(	O
with	O
two	O
exceptions	O
for	O
specific	O
markets	O
)	O
.	O
</s>
<s>
Before	O
the	O
introduction	O
of	O
System/360	B-Application
,	O
business	O
and	O
scientific	O
applications	O
used	O
different	O
computers	O
with	O
different	O
instruction	B-General_Concept
sets	I-General_Concept
and	O
operating	O
systems	O
.	O
</s>
<s>
Different-sized	O
computers	O
also	O
had	O
their	O
own	O
instruction	B-General_Concept
sets	I-General_Concept
.	O
</s>
<s>
IBM	O
was	O
the	O
first	O
manufacturer	O
to	O
exploit	O
microcode	B-Device
technology	O
to	O
implement	O
a	O
compatible	O
range	O
of	O
computers	O
of	O
widely	O
differing	O
performance	O
,	O
although	O
the	O
largest	O
,	O
fastest	O
models	O
had	O
hard-wired	O
logic	O
instead	O
.	O
</s>
<s>
The	O
least	O
expensive	O
model	O
was	O
the	O
Model	B-Device
20	I-Device
with	O
as	O
little	O
as	O
4096	O
bytes	B-Application
of	O
core	O
memory	O
,	O
eight	O
16-bit	O
registers	O
instead	O
of	O
the	O
sixteen	O
32-bit	O
registers	O
of	O
other	O
System/360	B-Application
models	O
,	O
and	O
an	O
instruction	B-General_Concept
set	I-General_Concept
that	O
was	O
a	O
subset	O
of	O
that	O
used	O
by	O
the	O
rest	O
of	O
the	O
range	O
.	O
</s>
<s>
The	O
initial	O
announcement	O
in	O
1964	O
included	O
Models	O
30	B-Device
,	O
40	B-Device
,	O
50	B-Device
,	O
60	O
,	O
62	O
,	O
and	O
70	O
.	O
</s>
<s>
The	O
first	O
three	O
were	O
low	O
-	O
to	O
middle-range	O
systems	O
aimed	O
at	O
the	O
IBM	B-Device
1400	I-Device
series	I-Device
market	O
.	O
</s>
<s>
The	O
last	O
three	O
,	O
intended	O
to	O
replace	O
the	O
7000	B-Device
series	I-Device
machines	O
,	O
never	O
shipped	O
and	O
were	O
replaced	O
with	O
the	O
65	B-Device
and	O
75	B-Device
,	O
which	O
were	O
first	O
delivered	O
in	O
November	O
1965	O
,	O
and	O
January	O
1966	O
,	O
respectively	O
.	O
</s>
<s>
Later	O
additions	O
to	O
the	O
low-end	O
included	O
models	O
20	B-Device
(	O
1966	O
,	O
mentioned	O
above	O
)	O
,	O
22	B-Device
(	O
1971	O
)	O
,	O
and	O
25	B-Device
(	O
1968	O
)	O
.	O
</s>
<s>
The	O
Model	B-Device
20	I-Device
had	O
several	O
sub-models	O
;	O
sub-model	O
5	O
was	O
at	O
the	O
higher	O
end	O
of	O
the	O
model	O
.	O
</s>
<s>
The	O
Model	O
22	B-Device
was	O
a	O
recycled	O
Model	B-Device
30	I-Device
with	O
minor	O
limitations	O
:	O
a	O
smaller	O
maximum	O
memory	O
configuration	O
,	O
and	O
slower	O
I/O	O
channels	O
,	O
which	O
limited	O
it	O
to	O
slower	O
and	O
lower-capacity	O
disk	B-Device
and	O
tape	O
devices	O
than	O
on	O
the	O
30	B-Device
.	O
</s>
<s>
The	O
Model	B-Device
44	I-Device
(	O
1966	O
)	O
was	O
a	O
specialized	O
model	O
,	O
designed	O
for	O
scientific	O
computing	O
and	O
for	O
real-time	O
computing	O
and	O
process	O
control	O
,	O
featuring	O
some	O
additional	O
instructions	O
,	O
and	O
with	O
all	O
storage-to-storage	O
instructions	O
and	O
five	O
other	O
complex	O
instructions	O
eliminated	O
.	O
</s>
<s>
A	O
succession	O
of	O
high-end	O
machines	O
included	O
the	O
Model	B-Device
67	I-Device
(	O
1966	O
,	O
mentioned	O
below	O
,	O
briefly	O
anticipated	O
as	O
the	O
64	O
and	O
66	O
)	O
,	O
85	B-Device
(	O
1969	O
)	O
,	O
91	B-Device
(	O
1967	O
,	O
anticipated	O
as	O
the	O
92	O
)	O
,	O
95	O
(	O
1968	O
)	O
,	O
and	O
195	B-Device
(	O
1971	O
)	O
.	O
</s>
<s>
The	O
85	B-Device
design	O
was	O
intermediate	O
between	O
the	O
System/360	B-Application
line	O
and	O
the	O
follow-on	O
System/370	B-Device
and	O
was	O
the	O
basis	O
for	O
the	O
370/165	O
.	O
</s>
<s>
There	O
was	O
a	O
System/370	B-Device
version	O
of	O
the	O
195	B-Device
,	O
but	O
it	O
did	O
not	O
include	O
Dynamic	B-Architecture
Address	I-Architecture
Translation	I-Architecture
.	O
</s>
<s>
The	O
implementations	O
differed	O
substantially	O
,	O
using	O
different	O
native	O
data	O
path	O
widths	O
,	O
presence	O
or	O
absence	O
of	O
microcode	B-Device
,	O
yet	O
were	O
extremely	O
compatible	O
.	O
</s>
<s>
The	O
91	B-Device
,	O
for	O
example	O
,	O
was	O
designed	O
for	O
scientific	O
computing	O
and	O
provided	O
out-of-order	B-General_Concept
instruction	I-General_Concept
execution	I-General_Concept
(	O
and	O
could	O
yield	O
"	O
imprecise	O
interrupts	B-Application
"	O
if	O
a	O
program	O
trap	B-Application
occurred	O
while	O
several	O
instructions	O
were	O
being	O
read	O
)	O
,	O
but	O
lacked	O
the	O
decimal	O
instruction	B-General_Concept
set	I-General_Concept
used	O
in	O
commercial	O
applications	O
.	O
</s>
<s>
New	O
features	O
could	O
be	O
added	O
without	O
violating	O
architectural	O
definitions	O
:	O
the	O
65	B-Device
had	O
a	O
dual-processor	O
version	O
(	O
M65MP	O
)	O
with	O
extensions	O
for	O
inter-CPU	O
signalling	O
;	O
the	O
85	B-Device
introduced	O
cache	O
memory	O
.	O
</s>
<s>
Models	O
44	B-Device
,	O
75	B-Device
,	O
91	B-Device
,	O
95	O
,	O
and	O
195	B-Device
were	O
implemented	O
with	O
hardwired	O
logic	O
,	O
rather	O
than	O
microcoded	B-Device
as	O
all	O
other	O
models	O
.	O
</s>
<s>
The	O
Model	B-Device
67	I-Device
,	O
announced	O
in	O
August	O
1965	O
,	O
was	O
the	O
first	O
production	O
IBM	O
system	O
to	O
offer	O
dynamic	B-Architecture
address	I-Architecture
translation	I-Architecture
(	O
virtual	B-Architecture
memory	I-Architecture
)	O
hardware	O
to	O
support	O
time-sharing	B-General_Concept
.	O
</s>
<s>
"	O
DAT	O
"	O
is	O
now	O
more	O
commonly	O
referred	O
to	O
as	O
an	O
MMU	B-General_Concept
.	O
</s>
<s>
An	O
experimental	O
one-off	O
unit	O
was	O
built	O
based	O
on	O
a	O
model	B-Device
40	I-Device
.	O
</s>
<s>
Before	O
the	O
67	B-Device
,	O
IBM	O
had	O
announced	O
models	O
64	O
and	O
66	O
,	O
DAT	O
versions	O
of	O
the	O
60	O
and	O
62	O
,	O
but	O
they	O
were	O
almost	O
immediately	O
replaced	O
with	O
the	O
67	B-Device
at	O
the	O
same	O
time	O
that	O
the	O
60	O
and	O
62	O
were	O
replaced	O
with	O
the	O
65	B-Device
.	O
</s>
<s>
DAT	O
hardware	O
would	O
reappear	O
in	O
the	O
S/370	B-Device
series	O
in	O
1972	O
,	O
though	O
it	O
was	O
initially	O
absent	O
from	O
the	O
series	O
.	O
</s>
<s>
Like	O
its	O
close	O
relative	O
,	O
the	O
65	B-Device
,	O
the	O
67	B-Device
also	O
offered	O
dual	O
CPUs	O
.	O
</s>
<s>
IBM	O
stopped	O
marketing	O
all	O
System/360	B-Application
models	O
by	O
the	O
end	O
of	O
1977	O
.	O
</s>
<s>
IBM	O
's	O
existing	O
customers	O
had	O
a	O
large	O
investment	O
in	O
software	O
that	O
executed	O
on	O
second-generation	B-Device
machines	I-Device
.	O
</s>
<s>
Several	O
models	O
offered	O
the	O
option	O
of	O
emulation	B-Application
of	O
the	O
customer	O
's	O
previous	O
computer	O
using	O
a	O
combination	O
of	O
special	O
hardware	O
,	O
special	O
microcode	B-Device
and	O
an	O
emulation	B-Application
program	O
that	O
used	O
the	O
emulation	B-Application
instructions	O
to	O
simulate	O
the	O
target	O
system	O
,	O
so	O
that	O
old	O
programs	O
could	O
run	O
on	O
the	O
new	O
machine	O
.	O
</s>
<s>
Customers	O
initially	O
had	O
to	O
halt	O
the	O
computer	O
and	O
load	O
the	O
emulation	B-Application
program	O
.	O
</s>
<s>
IBM	O
later	O
added	O
features	O
and	O
modified	O
emulator	B-Application
programs	O
to	O
allow	O
emulation	B-Application
of	O
the	O
1401	B-Device
,	O
1440	B-Device
,	O
1460	B-Device
,	O
1410	B-Device
and	O
7010	B-Device
under	O
the	O
control	O
of	O
an	O
operating	O
system	O
.	O
</s>
<s>
The	O
Model	O
85	B-Device
and	O
later	O
System/370	B-Device
maintained	O
the	O
precedent	O
,	O
retaining	O
emulation	B-Application
options	O
and	O
allowing	O
emulator	B-Application
programs	O
to	O
execute	O
under	O
operating	O
system	O
control	O
alongside	O
native	O
programs	O
.	O
</s>
<s>
System/360	B-Application
(	O
excepting	O
the	O
Models	O
20	B-Device
,	O
44	B-Device
and	O
67	B-Device
)	O
was	O
replaced	O
with	O
the	O
compatible	O
System/370	B-Device
range	O
in	O
1970	O
and	O
Model	B-Device
20	I-Device
users	O
were	O
targeted	O
to	O
move	O
to	O
the	O
IBM	B-Device
System/3	I-Device
.	O
</s>
<s>
(	O
The	O
idea	O
of	O
a	O
major	O
breakthrough	O
with	O
FS	B-Device
technology	I-Device
was	O
dropped	O
in	O
the	O
mid-1970s	O
for	O
cost-effectiveness	O
and	O
continuity	O
reasons	O
.	O
)	O
</s>
<s>
Later	O
compatible	O
IBM	O
systems	O
include	O
the	O
4300	B-Device
family	I-Device
,	O
the	O
308x	B-Device
family	I-Device
,	O
the	O
3090	B-Device
,	O
the	O
ES/9000	B-Device
and	O
9672	O
families	O
(	O
System/390	B-Device
family	O
)	O
,	O
and	O
the	O
IBM	B-Device
Z	I-Device
series	O
.	O
</s>
<s>
Computers	O
that	O
were	O
mostly	O
identical	O
or	O
compatible	O
in	O
terms	O
of	O
the	O
machine	O
code	O
or	O
architecture	B-General_Concept
of	O
the	O
System/360	B-Application
included	O
Amdahl	O
's	O
470	O
family	O
(	O
and	O
its	O
successors	O
)	O
,	O
Hitachi	O
mainframes	B-Architecture
,	O
the	O
UNIVAC	B-Device
9000	I-Device
series	I-Device
,	O
Fujitsu	O
as	O
the	O
Facom	O
,	O
the	O
RCA	B-Device
Spectra	I-Device
70	I-Device
series	O
,	O
and	O
the	O
English	B-Device
Electric	I-Device
System	I-Device
4	I-Device
.	O
</s>
<s>
UNIVAC	O
also	O
developed	O
the	O
UNIVAC	B-Device
Series	I-Device
90	I-Device
as	O
successors	O
to	O
the	O
9000	O
series	O
and	O
Series	O
70	O
.	O
</s>
<s>
The	O
Soviet	O
Union	O
produced	O
a	O
System/360	B-Application
clone	O
named	O
the	O
ES	B-Device
EVM	I-Device
.	O
</s>
<s>
The	O
IBM	B-Device
5100	I-Device
portable	O
computer	O
,	O
introduced	O
in	O
1975	O
,	O
offered	O
an	O
option	O
to	O
execute	O
the	O
System/360	B-Application
'	O
s	O
APL.SV	B-Language
programming	I-Language
language	I-Language
through	O
a	O
hardware	O
emulator	B-Application
.	O
</s>
<s>
IBM	O
used	O
this	O
approach	O
to	O
avoid	O
the	O
costs	O
and	O
delay	O
of	O
creating	O
a	O
5100-specific	O
version	O
of	O
APL	B-Language
.	O
</s>
<s>
Special	O
radiation-hardened	O
and	O
otherwise	O
somewhat	O
modified	O
System/360s	B-Application
,	O
in	O
the	O
form	O
of	O
the	O
System/4	B-Device
Pi	I-Device
avionics	O
computer	O
,	O
are	O
used	O
in	O
several	O
fighter	O
and	O
bomber	O
jet	O
aircraft	O
.	O
</s>
<s>
In	O
the	O
complete	O
32-bit	O
AP-101	O
version	O
,	O
4	O
Pi	O
machines	O
were	O
used	O
as	O
the	O
replicated	O
computing	O
nodes	O
of	O
the	O
fault-tolerant	B-General_Concept
Space	O
Shuttle	O
computer	O
system	O
(	O
in	O
five	O
nodes	O
)	O
.	O
</s>
<s>
The	O
U.S.	O
Federal	O
Aviation	O
Administration	O
operated	O
the	O
IBM	B-Device
9020	I-Device
,	O
a	O
special	O
cluster	O
of	O
modified	O
System/360s	B-Application
for	O
air	O
traffic	O
control	O
,	O
from	O
1970	O
until	O
the	O
1990s	O
.	O
</s>
<s>
(	O
Some	O
9020	O
software	O
is	O
apparently	O
still	O
used	O
via	O
emulation	B-Application
on	O
newer	O
hardware	O
.	O
)	O
</s>
<s>
Commercialperformance(kIPS )	O
Using	O
commercial	O
instruction	O
mix	O
(	O
"	O
ADP	O
Mix	O
"	O
)	O
CPUBandwidth( 	O
MB/sec	O
)	O
Memorybandwidth( 	O
MB/sec	O
)	O
Memory	O
size( in	O
(	O
binary	O
)	O
KB	O
)	O
Weight(lbs )	O
Notes	O
30	B-Device
Apr	O
1964	O
Jun	O
1965	O
10.2	O
29	O
1.3	O
0.7	O
8	O
–	O
64	O
40	B-Device
Apr	O
1964	O
Apr	O
1965	O
40	B-Device
75	B-Device
3.2	O
0.8	O
16	O
–	O
256	O
depends	O
on	O
memory	O
50	B-Device
Apr	O
1964	O
Aug	O
1965	O
133	O
169	O
8.0	O
2.0	O
64	O
–	O
512	O
depends	O
on	O
memory	O
Supported	O
IBM	B-Device
2361	I-Device
Large	I-Device
Capacity	I-Device
Storage	I-Device
(	O
LCS	B-Device
)	O
.	O
</s>
<s>
60	O
and	O
62	O
Apr	O
1964	O
data-sort-value	O
=	O
"	O
991231	O
"	O
Replaced	O
by	O
Model	B-Device
65	I-Device
70	O
Apr	O
1964	O
data-sort-value	O
=	O
"	O
991231	O
"	O
Replaced	O
by	O
Model	O
75	B-Device
90	O
Apr	O
1964	O
data-sort-value	O
=	O
"	O
991231	O
"	O
Replaced	O
by	O
Model	O
92	O
92	O
Aug	O
1964	O
data-sort-value	O
=	O
"	O
991231	O
"	O
Redesignated	O
as	O
IBM	B-Device
System/360	I-Device
Model	I-Device
91	I-Device
20	B-Device
Nov	O
1964	O
Mar	O
1966	O
2.0	O
2.6	O
4-32	O
16-bit	O
,	O
low	O
end	O
,	O
limited	O
partially	O
incompatible	O
instruction	B-General_Concept
set	I-General_Concept
91	B-Device
Jan	O
1966	O
Oct	O
1967	O
1,900	O
1,800	O
133	O
164	O
1,024	O
-4	O
,	O
096	O
Available	O
on	O
special	O
bid	O
beginning	O
Nov	O
1964	O
64	O
and	O
66	O
Apr	O
1965	O
data-sort-value	O
=	O
"	O
991231	O
"	O
Replaced	O
by	O
Model	B-Device
67	I-Device
65	B-Device
Apr	O
1965	O
Nov	O
1965	O
563	O
567	O
40	B-Device
21	O
128-1	O
,	O
024	O
depends	O
on	O
memory	O
and	O
number	O
of	O
processors	O
Supported	O
LCS	B-Device
75	B-Device
Apr	O
1965	O
Jan	O
1966	O
940	O
670	O
41	O
43	O
256-1	O
,	O
024	O
depends	O
on	O
memory	O
Supported	O
LCS	B-Device
67	B-Device
Aug	O
1965	O
May	O
1966	O
40	B-Device
21	O
512-2	O
,	O
048	O
-	O
Processor	O
only	O
Dynamic	B-Architecture
address	I-Architecture
translation	I-Architecture
for	O
time	B-General_Concept
sharing	I-General_Concept
44	B-Device
Aug	O
1965	O
Sep	O
1966	O
118	O
185	O
16	O
4.0	O
32-256	O
depends	O
on	O
memory	O
Specialized	O
for	O
scientific	O
computing	O
95	O
special	O
order	O
Feb	O
1968	O
3,800	O
est	O
.	O
</s>
<s>
133	O
711	O
5,220	O
Performance	O
estimated	O
as	O
2×	O
Model	B-Device
91	I-Device
25	B-Device
Jan	O
1968	O
Oct	O
1968	O
9.7	O
25	B-Device
1.1	O
2.2	O
16-48	O
85	B-Device
Jan	O
1968	O
Dec	O
1969	O
3,245	O
3,418	O
100	O
67	B-Device
512	O
–	O
4,096	O
-	O
Processor	O
only	O
16	O
–	O
32	O
KB	O
cache	O
memory	O
,	O
extended-precision	O
floating	B-Algorithm
point	I-Algorithm
.	O
</s>
<s>
195	B-Device
Aug	O
1969	O
Mar	O
1971	O
10,000	O
est	O
.	O
</s>
<s>
Performance	O
estimated	O
as	O
3×	O
Model	O
85	B-Device
.	O
</s>
<s>
Six	O
of	O
the	O
twenty	O
IBM	B-Application
System/360	I-Application
models	O
announced	O
either	O
were	O
never	O
shipped	O
or	O
were	O
never	O
released	O
.	O
</s>
<s>
Fourteen	O
of	O
the	O
twenty	O
IBM	B-Application
System/360	I-Application
models	O
announced	O
shipped	O
.	O
</s>
<s>
The	O
System/360	B-Application
introduced	O
a	O
number	O
of	O
industry	O
standards	O
to	O
the	O
marketplace	O
,	O
such	O
as	O
:	O
</s>
<s>
The	O
8-bit	O
byte	B-Application
(	O
against	O
financial	O
pressure	O
during	O
development	O
to	O
reduce	O
the	O
byte	B-Application
to	O
4	O
or	O
6	O
bits	O
)	O
,	O
rather	O
than	O
adopting	O
the	O
7030	B-Device
concept	O
of	O
accessing	O
bytes	B-Application
of	O
variable	O
size	O
at	O
arbitrary	O
bit	O
addresses	O
.	O
</s>
<s>
The	O
System/360	B-Application
series	O
has	O
a	O
computer	B-General_Concept
system	I-General_Concept
architecture	I-General_Concept
specification	O
.	O
</s>
<s>
The	O
architecture	B-General_Concept
describes	O
mandatory	O
interfaces	O
that	O
must	O
be	O
available	O
on	O
all	O
implementations	O
,	O
and	O
optional	O
interfaces	O
.	O
</s>
<s>
Some	O
aspects	O
of	O
this	O
architecture	B-General_Concept
are	O
:	O
</s>
<s>
An	O
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
All	O
models	O
of	O
System/360	B-Application
,	O
except	O
for	O
the	O
Model	B-Device
20	I-Device
and	O
Model	B-Device
44	I-Device
,	O
implemented	O
that	O
specification	O
.	O
</s>
<s>
If	O
the	O
Commercial	O
Instruction	B-General_Concept
Set	I-General_Concept
option	O
was	O
installed	O
,	O
packed	O
decimal	O
arithmetic	O
could	O
be	O
performed	O
as	O
memory-to-memory	O
with	O
some	O
memory-to-register	O
operations	O
.	O
</s>
<s>
The	O
Scientific	O
Instruction	B-General_Concept
Set	I-General_Concept
feature	O
,	O
if	O
installed	O
,	O
provided	O
access	O
to	O
four	O
floating-point	B-Algorithm
registers	O
that	O
could	O
be	O
programmed	O
for	O
either	O
32-bit	O
or	O
64-bit	B-Device
floating-point	B-Algorithm
operations	O
.	O
</s>
<s>
The	O
Models	O
85	B-Device
and	O
195	B-Device
could	O
also	O
operate	O
on	O
128-bit	O
extended-precision	O
floating-point	B-Algorithm
numbers	I-Algorithm
stored	O
in	O
pairs	O
of	O
floating-point	B-Algorithm
registers	O
,	O
and	O
software	O
provided	O
emulation	B-Application
in	O
other	O
models	O
.	O
</s>
<s>
The	O
System/360	B-Application
used	O
an	O
8-bit	O
byte	B-Application
,	O
32-bit	O
word	O
,	O
64-bit	B-Device
double-word	O
,	O
and	O
4-bit	O
nibble	O
.	O
</s>
<s>
Memory	B-General_Concept
addressing	I-General_Concept
was	O
accomplished	O
using	O
a	O
base-plus-displacement	O
scheme	O
,	O
with	O
registers	O
1	O
through	O
F	O
(	O
15	O
)	O
.	O
</s>
<s>
A	O
displacement	O
was	O
encoded	O
in	O
12	O
bits	O
,	O
thus	O
allowing	O
a	O
4096-byte	O
displacement	O
(	O
0	O
–	O
4095	O
)	O
,	O
as	O
the	O
offset	O
from	O
the	O
address	O
put	O
in	O
a	O
base	O
register	O
.	O
</s>
<s>
Register	O
0	O
could	O
not	O
be	O
used	O
as	O
a	O
base	O
register	O
nor	O
as	O
an	O
index	O
register	O
(	O
nor	O
as	O
a	O
branch	O
address	B-General_Concept
register	I-General_Concept
)	O
,	O
as	O
"	O
0	O
"	O
was	O
reserved	O
to	O
indicate	O
an	O
address	O
in	O
the	O
first	O
4KB	O
of	O
memory	O
,	O
that	O
is	O
,	O
if	O
register	O
0	O
was	O
specified	O
as	O
described	O
,	O
the	O
value	O
0x00000000	O
was	O
implicitly	O
input	O
to	O
the	O
effective	O
address	O
calculation	O
in	O
place	O
of	O
whatever	O
value	O
might	O
be	O
contained	O
within	O
register	O
0	O
(	O
or	O
if	O
specified	O
as	O
a	O
branch	O
address	B-General_Concept
register	I-General_Concept
,	O
then	O
no	O
branch	O
was	O
taken	O
,	O
and	O
the	O
content	O
of	O
register	O
0	O
was	O
ignored	O
,	O
but	O
any	O
side	O
effect	O
of	O
the	O
instruction	O
was	O
performed	O
)	O
.	O
</s>
<s>
This	O
specific	O
behavior	O
permitted	O
initial	O
execution	O
of	O
an	O
interrupt	B-Application
routines	O
,	O
since	O
base	O
registers	O
would	O
not	O
necessarily	O
be	O
set	O
to	O
0	O
during	O
the	O
first	O
few	O
instruction	O
cycles	O
of	O
an	O
interrupt	B-Application
routine	O
.	O
</s>
<s>
It	O
is	O
n't	O
needed	O
for	O
IPL	O
(	O
"	O
Initial	O
Program	O
Load	O
"	O
or	O
boot	B-Operating_System
)	O
,	O
as	O
one	O
can	O
always	O
clear	O
a	O
register	O
without	O
the	O
need	O
to	O
save	O
it	O
.	O
</s>
<s>
With	O
the	O
exception	O
of	O
the	O
Model	B-Device
67	I-Device
,	O
all	O
addresses	O
were	O
real	O
memory	O
addresses	O
.	O
</s>
<s>
Virtual	B-Architecture
memory	I-Architecture
was	O
not	O
available	O
in	O
most	O
IBM	O
mainframes	B-Architecture
until	O
the	O
System/370	B-Device
series	O
.	O
</s>
<s>
The	O
Model	B-Device
67	I-Device
introduced	O
a	O
virtual	B-Architecture
memory	I-Architecture
architecture	B-General_Concept
,	O
which	O
MTS	B-Application
,	O
CP-67	B-Application
,	O
and	O
TSS/360	B-Application
used	O
—	O
but	O
not	O
IBM	O
's	O
mainline	O
System/360	B-Application
operating	O
systems	O
.	O
</s>
<s>
The	O
System/360	B-Application
machine-code	O
instructions	O
are	O
2	O
bytes	B-Application
long	O
(	O
no	O
memory	O
operands	O
)	O
,	O
4	O
bytes	B-Application
long	O
(	O
one	O
operand	O
)	O
,	O
or	O
6	O
bytes	B-Application
long	O
(	O
two	O
operands	O
)	O
.	O
</s>
<s>
Instructions	O
are	O
always	O
situated	O
on	O
2-byte	O
boundaries	O
.	O
</s>
<s>
Operations	O
like	O
MVC	O
(	O
Move-Characters	O
)	O
(	O
Hex	O
:	O
D2	O
)	O
can	O
only	O
move	O
at	O
most	O
256	O
bytes	B-Application
of	O
information	O
.	O
</s>
<s>
Moving	O
more	O
than	O
256	O
bytes	B-Application
of	O
data	O
required	O
multiple	O
MVC	O
operations	O
.	O
</s>
<s>
(	O
The	O
System/370	B-Device
series	O
introduced	O
a	O
family	O
of	O
more	O
powerful	O
instructions	O
such	O
as	O
the	O
MVCL	O
"	O
Move-Characters-Long	O
"	O
instruction	O
,	O
which	O
supports	O
moving	O
up	O
to	O
16MB	O
as	O
a	O
single	O
block	O
.	O
)	O
</s>
<s>
An	O
operand	O
is	O
two	O
bytes	B-Application
long	O
,	O
typically	O
representing	O
an	O
address	O
as	O
a	O
4-bit	O
nibble	O
denoting	O
a	O
base	O
register	O
and	O
a	O
12-bit	O
displacement	O
relative	O
to	O
the	O
contents	O
of	O
that	O
register	O
,	O
in	O
the	O
range	O
(	O
shown	O
here	O
as	O
hexadecimal	B-Device
numbers	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
an	O
MVC	O
instruction	O
that	O
moves	O
256	O
bytes	B-Application
(	O
with	O
length	O
code	O
255	O
in	O
hexadecimal	B-Device
as	O
)	O
from	O
base	O
register	O
7	O
,	O
plus	O
displacement	O
,	O
to	O
base	O
register	O
8	O
,	O
plus	O
displacement	O
,	O
would	O
be	O
coded	O
as	O
the	O
6-byte	O
instruction	O
""	O
(	O
operator/length/address1/address2	O
)	O
.	O
</s>
<s>
The	O
System/360	B-Application
was	O
designed	O
to	O
separate	O
the	O
system	O
state	O
from	O
the	O
problem	O
state	O
.	O
</s>
<s>
A	O
channel	O
is	O
a	O
specialized	O
processor	O
with	O
the	O
instruction	B-General_Concept
set	I-General_Concept
optimized	O
for	O
transferring	O
data	O
between	O
a	O
peripheral	O
and	O
main	O
memory	O
.	O
</s>
<s>
In	O
modern	O
terms	O
,	O
this	O
could	O
be	O
compared	O
to	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
.	O
</s>
<s>
The	O
S/360	B-Application
connects	O
channels	O
to	O
control	O
units	O
with	O
bus	B-Device
and	I-Device
tag	I-Device
cables	O
;	O
IBM	O
eventually	O
replaced	O
these	O
with	O
(	B-Device
Enterprise	I-Device
Systems	I-Device
Connection	I-Device
(	O
ESCON	B-Device
)	O
and	O
Fibre	B-Architecture
Connection	I-Architecture
(	O
FICON	B-Architecture
)	O
channels	O
.	O
</s>
<s>
There	O
were	O
initially	O
two	O
types	O
of	O
channels	O
;	O
byte-multiplexer	O
channels	O
(	O
known	O
at	O
the	O
time	O
simply	O
as	O
"	O
multiplexor	O
channels	O
"	O
)	O
,	O
for	O
connecting	O
"	O
slow	O
speed	O
"	O
devices	O
such	O
as	O
card	O
readers	O
and	O
punches	O
,	O
line	O
printers	O
,	O
and	O
communications	O
controllers	O
,	O
and	O
selector	O
channels	O
for	O
connecting	O
high	O
speed	O
devices	O
,	O
such	O
as	O
disk	B-Device
drives	I-Device
,	O
tape	O
drives	O
,	O
data	B-Device
cells	I-Device
and	O
drums	B-General_Concept
.	O
</s>
<s>
Every	O
System/360	B-Application
(	O
except	O
for	O
the	O
Model	B-Device
20	I-Device
,	O
which	O
was	O
not	O
a	O
standard	O
360	O
)	O
has	O
a	O
byte-multiplexer	O
channel	O
and	O
1	O
or	O
more	O
selector	O
channels	O
,	O
though	O
the	O
model	O
25	B-Device
has	O
just	O
one	O
channel	O
,	O
which	O
can	O
be	O
either	O
a	O
byte-multiplexor	O
or	O
selector	O
channel	O
.	O
</s>
<s>
The	O
smaller	O
models	O
(	O
up	O
to	O
the	O
model	O
50	B-Device
)	O
have	O
integrated	O
channels	O
,	O
while	O
for	O
the	O
larger	O
models	O
(	O
model	B-Device
65	I-Device
and	O
above	O
)	O
the	O
channels	O
are	O
large	O
separate	O
units	O
in	O
separate	O
cabinets	O
:	O
the	O
IBM	O
2870	O
is	O
the	O
byte-multiplexor	O
channel	O
with	O
up	O
to	O
four	O
selector	O
sub-channels	O
,	O
and	O
the	O
IBM	O
2860	O
is	O
up	O
to	O
three	O
selector	O
channels	O
.	O
</s>
<s>
The	O
byte-multiplexer	O
channel	O
is	O
able	O
to	O
handle	O
I/O	O
to/from	O
several	O
devices	O
simultaneously	O
at	O
the	O
device	O
's	O
highest	O
rated	O
speeds	O
,	O
hence	O
the	O
name	O
,	O
as	O
it	O
multiplexed	B-Architecture
I/O	O
from	O
those	O
devices	O
onto	O
a	O
single	O
data	O
path	O
to	O
main	O
memory	O
.	O
</s>
<s>
Devices	O
connected	O
to	O
a	O
byte-multiplexer	O
channel	O
are	O
configured	O
to	O
operate	O
in	O
1-byte	O
,	O
2-byte	O
,	O
4-byte	O
,	O
or	O
"	O
burst	O
"	O
mode	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
2501	O
card	B-Architecture
reader	I-Architecture
operating	O
at	O
600	O
cards	O
per	O
minute	O
would	O
be	O
in	O
1-byte	O
mode	O
,	O
while	O
a	O
1403-N1	O
printer	O
would	O
be	O
in	O
burst	O
mode	O
.	O
</s>
<s>
Also	O
,	O
the	O
byte-multiplexer	O
channels	O
on	O
larger	O
models	O
have	O
an	O
optional	O
selector	O
subchannel	O
section	O
that	O
would	O
accommodate	O
tape	O
drives	O
.	O
</s>
<s>
The	O
byte-multiplexor	O
'	O
s	O
channel	O
address	O
was	O
typically	O
"	O
0	O
"	O
and	O
the	O
selector	O
subchannel	O
addresses	O
were	O
from	O
"	O
C0	O
"	O
to	O
"	O
FF.	O
"	O
</s>
<s>
Thus	O
,	O
tape	O
drives	O
on	O
System/360	B-Application
were	O
commonly	O
addressed	O
at	O
0C0	O
–	O
0C7	O
.	O
</s>
<s>
Other	O
common	O
byte-multiplexer	O
addresses	O
are	O
:	O
00A	O
:	O
2501	O
Card	B-Architecture
Reader	I-Architecture
,	O
00C/00D	O
:	O
2540	O
Reader/Punch	O
,	O
00E/00F	O
:	O
1403-N1	O
Printers	O
,	O
010	O
–	O
013	O
:	O
3211	O
Printers	O
,	O
020	O
–	O
0BF	O
:	O
2701/2703	B-Device
Telecommunications	O
Units	O
.	O
</s>
<s>
These	O
addresses	O
are	O
still	O
commonly	O
used	O
in	O
z/VM	B-Application
virtual	B-Architecture
machines	I-Architecture
.	O
</s>
<s>
System/360	B-Application
models	O
40	B-Device
and	O
50	B-Device
have	O
an	O
integrated	O
1052-7	O
console	B-Device
that	O
is	O
usually	O
addressed	O
as	O
01F	O
,	O
however	O
,	O
this	O
was	O
not	O
connected	O
to	O
the	O
byte-multiplexer	O
channel	O
,	O
but	O
rather	O
,	O
had	O
a	O
direct	O
internal	O
connection	O
to	O
the	O
mainframe	B-Architecture
.	O
</s>
<s>
The	O
model	B-Device
30	I-Device
attached	O
a	O
different	O
model	O
of	O
1052	O
through	O
a	O
1051	O
control	O
unit	O
.	O
</s>
<s>
The	O
models	O
60	O
through	O
75	B-Device
also	O
use	O
the	O
1052-7	O
.	O
</s>
<s>
Control	O
units	O
are	O
connected	O
to	O
the	O
channels	O
with	O
"	O
bus	B-Device
and	I-Device
tag	I-Device
"	O
cable	O
pairs	O
.	O
</s>
<s>
The	O
general	O
configuration	O
of	O
a	O
channel	O
is	O
to	O
connect	O
the	O
devices	O
in	O
a	O
chain	O
,	O
like	O
this	O
:	O
Mainframe	B-Architecture
—	O
Control	O
Unit	O
X	O
—	O
Control	O
Unit	O
Y	O
—	O
Control	O
Unit	O
Z	O
.	O
</s>
<s>
For	O
example	O
,	O
control	O
unit	O
X	O
might	O
capture	O
addresses	O
40	B-Device
–	O
4F	O
,	O
control	O
unit	O
Y	O
:	O
C0	O
–	O
DF	O
,	O
and	O
control	O
unit	O
Z	O
:	O
80	O
–	O
9F	O
.	O
</s>
<s>
For	O
example	O
,	O
you	O
could	O
have	O
control	O
unit	O
Y	O
with	O
6	O
disks	B-Device
,	O
that	O
would	O
be	O
addressed	O
as	O
C0-C5	O
.	O
</s>
<s>
When	O
a	O
device	O
selection	O
was	O
sent	O
out	O
on	O
a	O
mainframe	B-Architecture
's	O
channel	O
,	O
the	O
selection	O
was	O
sent	O
from	O
X->Y->Z->Y->X	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
have	O
multiple	O
channels	O
attached	O
to	O
a	O
control	O
unit	O
from	O
the	O
same	O
or	O
multiple	O
mainframes	B-Architecture
,	O
thus	O
providing	O
a	O
rich	O
high-performance	O
,	O
multiple-access	O
,	O
and	O
backup	O
capability	O
.	O
</s>
<s>
IBM	O
first	O
introduced	O
a	O
new	O
type	O
of	O
I/O	O
channel	O
on	O
the	O
Model	O
85	B-Device
and	O
Model	O
195	B-Device
,	O
the	O
2880	O
block	O
multiplexer	O
channel	O
,	O
and	O
then	O
made	O
them	O
standard	O
on	O
the	O
System/370	B-Device
.	O
</s>
<s>
A	O
block	O
multiplexer	O
channel	O
can	O
support	O
either	O
standard	O
1.5MB/second	O
connections	O
or	O
,	O
with	O
the	O
2-byte	O
interface	O
feature	O
,	O
3MB/second	O
;	O
the	O
latter	O
use	O
one	O
tag	O
cable	O
and	O
two	O
bus	O
cables	O
.	O
</s>
<s>
On	O
the	O
S/370	B-Device
there	O
is	O
an	O
option	O
for	O
a	O
3.0	O
MB/s	O
data	O
streaming	O
channel	O
with	O
one	O
bus	O
cable	O
and	O
one	O
tag	O
cable	O
.	O
</s>
<s>
The	O
initial	O
use	O
for	O
this	O
was	O
the	O
2305	O
fixed-head	O
disk	B-Device
,	O
which	O
has	O
8	O
"	O
exposures	O
"	O
(	O
alias	O
addresses	O
)	O
and	O
rotational	O
position	O
sensing	O
(	O
RPS	O
)	O
.	O
</s>
<s>
Resistors	O
were	O
silk	O
screened	O
on	O
and	O
discrete	O
glass	O
encapsulated	O
transistors	B-Application
and	O
diodes	O
were	O
added	O
.	O
</s>
<s>
The	O
substrate	O
was	O
then	O
covered	O
with	O
a	O
metal	O
lid	O
or	O
encapsulated	O
in	O
plastic	O
to	O
create	O
a	O
"	O
Solid	B-Algorithm
Logic	I-Algorithm
Technology	I-Algorithm
"	O
(	O
SLT	O
)	O
module	O
.	O
</s>
<s>
A	O
number	O
of	O
these	O
were	O
then	O
flip	B-Device
chip	I-Device
mounted	O
onto	O
a	O
small	O
multi-layer	O
printed	O
circuit	O
"	O
SLT	B-Algorithm
card	I-Algorithm
"	O
.	O
</s>
<s>
The	O
smaller	O
System/360	B-Application
models	O
used	O
the	O
Basic	O
Operating	B-Application
System/360	I-Application
(	O
BOS/360	B-Application
)	O
,	O
Tape	O
Operating	O
System	O
(	O
TOS/360	B-Application
)	O
,	O
or	O
Disk	B-Device
Operating	B-Application
System/360	I-Application
(	O
DOS/360	O
,	O
which	O
evolved	O
into	O
DOS/VS	O
,	O
DOS/VSE	B-Application
,	O
VSE/AF	O
,	O
VSE/SP	O
,	O
VSE/ESA	O
,	O
and	O
then	O
z/VSE	B-Application
)	O
.	O
</s>
<s>
The	O
larger	O
models	O
used	O
Operating	B-Application
System/360	I-Application
(	O
OS/360	B-Application
)	O
.	O
</s>
<s>
IBM	O
developed	O
several	O
levels	O
of	O
OS/360	B-Application
,	O
with	O
increasingly	O
powerful	O
features	O
:	O
Primary	O
Control	O
Program	O
(	O
PCP	O
)	O
,	O
Multiprogramming	O
with	O
a	O
Fixed	O
number	O
of	O
Tasks	O
(	O
MFT	O
)	O
,	O
and	O
Multiprogramming	O
with	O
a	O
Variable	O
number	O
of	O
Tasks	O
(	O
MVT	O
)	O
.	O
</s>
<s>
PCP	O
was	O
used	O
on	O
intermediate	O
machines	O
too	O
small	O
to	O
run	O
MFT	O
well	O
,	O
and	O
on	O
larger	O
machines	O
before	O
MFT	O
was	O
available	O
;	O
the	O
final	O
releases	O
of	O
OS/360	B-Application
included	O
only	O
MFT	O
and	O
MVT	O
.	O
</s>
<s>
For	O
the	O
System/370	B-Device
and	O
later	O
machines	O
,	O
MFT	O
evolved	O
into	O
OS/VS1	B-Application
,	O
while	O
MVT	O
evolved	O
into	O
OS/VS2	B-Application
(	O
SVS	O
)	O
(	O
Single	O
Virtual	B-Architecture
Storage	I-Architecture
)	O
,	O
then	O
various	O
versions	O
of	O
MVS	B-Application
(	O
Multiple	B-Application
Virtual	I-Application
Storage	I-Application
)	O
culminating	O
in	O
the	O
current	O
z/OS	B-Application
.	O
</s>
<s>
When	O
it	O
announced	O
the	O
Model	B-Device
67	I-Device
in	O
August	O
1965	O
,	O
IBM	O
also	O
announced	O
TSS/360	B-Application
(	O
Time-Sharing	B-General_Concept
System	I-General_Concept
)	O
for	O
delivery	O
at	O
the	O
same	O
time	O
as	O
the	O
67	B-Device
.	O
</s>
<s>
TSS/360	B-Application
,	O
a	O
response	O
to	O
Multics	B-Application
,	O
was	O
an	O
ambitious	O
project	O
that	O
included	O
many	O
advanced	O
features	O
.	O
</s>
<s>
Customers	O
migrated	O
to	O
CP-67	B-Application
,	O
MTS	B-Application
(	O
Michigan	B-Application
Terminal	I-Application
System	I-Application
)	O
,	O
TSO	O
(	O
Time	B-Application
Sharing	I-Application
Option	I-Application
for	O
OS/360	B-Application
)	O
,	O
or	O
one	O
of	O
several	O
other	O
time-sharing	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
CP-67	B-Application
,	O
the	O
original	O
virtual	B-Architecture
machine	I-Architecture
system	O
,	O
was	O
also	O
known	O
as	O
CP/CMS	B-Application
.	O
</s>
<s>
CP/67	O
was	O
developed	O
outside	O
the	O
IBM	O
mainstream	O
at	O
IBM	O
's	O
Cambridge	O
Scientific	O
Center	O
,	O
in	O
cooperation	O
with	O
MIT	O
researchers	O
.	O
</s>
<s>
CP/CMS	B-Application
eventually	O
won	O
wide	O
acceptance	O
,	O
and	O
led	O
to	O
the	O
development	O
of	O
VM/370	B-Application
(	O
Virtual	B-Architecture
Machine	I-Architecture
)	O
which	O
had	O
a	O
primary	O
interactive	O
"	O
sub	O
"	O
operating	O
system	O
known	O
as	O
VM/CMS	B-Application
(	O
Conversational	O
Monitoring	O
System	O
)	O
.	O
</s>
<s>
This	O
evolved	O
into	O
today	O
's	O
z/VM	B-Application
.	O
</s>
<s>
The	O
Model	B-Device
20	I-Device
offered	O
a	O
simplified	O
and	O
rarely	O
used	O
tape-based	O
system	O
called	O
TPS	O
(	O
Tape	O
Processing	O
System	O
)	O
,	O
and	O
DPS	O
(	O
Disk	B-Device
Processing	O
System	O
)	O
that	O
provided	O
support	O
for	O
the	O
2311	O
disk	B-Device
drive	I-Device
.	O
</s>
<s>
TPS	O
could	O
run	O
on	O
a	O
machine	O
with	O
8KB	O
of	O
memory	O
;	O
DPS	O
required	O
12KB	O
,	O
which	O
was	O
pretty	O
hefty	O
for	O
a	O
Model	B-Device
20	I-Device
.	O
</s>
<s>
With	O
TPS	O
and	O
DPS	O
,	O
the	O
card	B-Architecture
reader	I-Architecture
was	O
used	O
to	O
read	O
the	O
Job	B-Application
Control	I-Application
Language	I-Application
cards	O
that	O
defined	O
the	O
stack	O
of	O
jobs	O
to	O
run	O
and	O
to	O
read	O
in	O
transaction	O
data	O
such	O
as	O
customer	O
payments	O
.	O
</s>
<s>
The	O
operating	O
system	O
was	O
held	O
on	O
tape	O
or	O
disk	B-Device
,	O
and	O
results	O
could	O
also	O
be	O
stored	O
on	O
the	O
tapes	O
or	O
hard	O
drives	O
.	O
</s>
<s>
A	O
little-known	O
and	O
little-used	O
suite	O
of	O
80-column	O
punched-card	B-Architecture
utility	O
programs	O
known	O
as	O
Basic	B-Application
Programming	I-Application
Support	I-Application
(	O
BPS	O
)	O
(	O
jocularly	O
:	O
Barely	O
Programming	O
Support	O
)	O
,	O
a	O
precursor	O
of	O
TOS	O
,	O
was	O
available	O
for	O
smaller	O
systems	O
.	O
</s>
<s>
IBM	O
created	O
a	O
new	O
naming	O
system	O
for	O
the	O
new	O
components	O
created	O
for	O
System/360	B-Application
,	O
although	O
well-known	O
old	O
names	O
,	O
like	O
IBM	B-Device
1403	I-Device
and	O
IBM	B-Device
1052	I-Device
,	O
were	O
retained	O
.	O
</s>
<s>
20xx	O
:	O
Arithmetic	O
processors	O
,	O
for	O
example	O
the	O
IBM	B-Device
2030	I-Device
,	O
which	O
was	O
the	O
CPU	O
for	O
the	O
IBM	B-Device
System/360	I-Device
Model	I-Device
30	I-Device
.	O
</s>
<s>
22xx	O
:	O
Visual	O
output	O
devices	O
,	O
for	O
example	O
the	O
IBM	B-Device
2250	I-Device
and	O
IBM	B-Device
2260	I-Device
CRT	O
displays	O
,	O
and	O
the	O
IBM	O
2203	O
line	O
printer	O
for	O
the	O
System/360	B-Application
model	B-Device
20	I-Device
.	O
</s>
<s>
23xx	O
:	O
Direct-access	B-Application
storage	I-Application
devices	I-Application
,	O
for	O
example	O
the	O
IBM	B-Device
2311	I-Device
and	O
IBM	B-Device
2314	I-Device
disk	B-Device
drives	I-Device
,	O
the	O
IBM	B-Device
2321	I-Device
Data	I-Device
Cell	I-Device
;	O
Main	O
storage	O
such	O
as	O
the	O
IBM	B-Device
2361	I-Device
Large	I-Device
Capacity	I-Device
Storage	I-Device
(	O
Core	O
Storage	O
,	O
Large	O
Core	O
Storage	O
or	O
LCS	B-Device
)	O
and	O
the	O
IBM	B-Device
2365	I-Device
Processor	I-Device
Storage	I-Device
.	O
</s>
<s>
25xx	O
:	O
Punched	B-Architecture
card	I-Architecture
handling	O
equipment	O
,	O
for	O
example	O
the	O
IBM	B-Device
2501	I-Device
(	O
card	B-Architecture
reader	I-Architecture
)	O
,	O
IBM	O
2520	O
(	O
card	O
punch	O
)	O
;	O
IBM	B-Device
2540	I-Device
(	O
reader/punch	O
)	O
and	O
IBM	O
2560	O
(	O
Multi-Function	O
Card	O
Machine	O
or	O
MFCM	O
)	O
.	O
</s>
<s>
27xx	O
:	O
Communications	O
equipment	O
,	O
for	O
example	O
the	O
IBM	B-Device
2701	I-Device
,	O
IBM	O
2705	O
,	O
IBM	O
2741	O
interactive	O
terminal	O
and	O
the	O
IBM	O
2780	O
batch	O
terminal	O
.	O
</s>
<s>
28xx	O
:	O
Channels	O
and	O
controllers	O
,	O
for	O
example	O
the	O
IBM	B-Device
2821	I-Device
Control	I-Device
Unit	I-Device
,	O
IBM	O
2841	O
and	O
IBM	O
2844	O
.	O
</s>
<s>
IBM	O
developed	O
a	O
new	O
family	O
of	O
peripheral	O
equipment	O
for	O
System/360	B-Application
,	O
carrying	O
over	O
a	O
few	O
from	O
its	O
older	O
1400	O
series	O
.	O
</s>
<s>
In	O
addition	O
,	O
System/360	B-Application
computers	O
could	O
use	O
certain	O
peripherals	O
that	O
were	O
originally	O
developed	O
for	O
earlier	O
computers	O
.	O
</s>
<s>
These	O
earlier	O
peripherals	O
used	O
a	O
different	O
numbering	O
system	O
,	O
such	O
as	O
the	O
IBM	B-Device
1403	I-Device
chain	O
printer	O
.	O
</s>
<s>
The	O
1403	O
,	O
an	O
extremely	O
reliable	O
device	O
that	O
had	O
already	O
earned	O
a	O
reputation	O
as	O
a	O
workhorse	O
,	O
was	O
sold	O
as	O
the	O
1403-N1	O
when	O
adapted	O
for	O
the	O
System/360	B-Application
.	O
</s>
<s>
Also	O
available	O
were	O
optical	B-Application
character	I-Application
recognition	I-Application
(	O
OCR	O
)	O
readers	O
IBM	O
1287	O
and	O
IBM	O
1288	O
which	O
could	O
read	O
Alpha	O
Numeric	B-Algorithm
(	O
A/N	O
)	O
and	O
Numeric	B-Algorithm
Hand	O
Printed	O
(	O
NHP/NHW	O
)	O
Characters	O
from	O
Cashier	O
's	O
rolls	O
of	O
tape	O
to	O
full	O
legal	O
size	O
pages	O
.	O
</s>
<s>
Models	O
65	B-Device
and	O
below	O
sold	O
with	O
an	O
IBM	O
1052-7	O
as	O
the	O
console	B-Device
typewriter	O
.	O
</s>
<s>
The	O
360/85	B-Device
with	O
feature	O
5450	O
uses	O
a	O
display	O
console	B-Device
that	O
was	O
not	O
compatible	O
with	O
anything	O
else	O
in	O
the	O
line	O
;	O
the	O
later	O
3066	O
console	B-Device
for	O
the	O
370/165	O
and	O
370/168	O
use	O
the	O
same	O
basic	O
display	O
design	O
as	O
the	O
360/85	B-Device
.	O
</s>
<s>
The	O
IBM	B-Application
System/360	I-Application
models	O
91	B-Device
and	O
195	B-Device
use	O
a	O
graphical	O
display	O
similar	O
to	O
the	O
IBM	B-Device
2250	I-Device
as	O
their	O
primary	O
console	B-Device
.	O
</s>
<s>
Certain	O
high-end	O
machines	O
could	O
optionally	O
be	O
purchased	O
with	O
a	O
2250	B-Device
graphical	O
display	O
,	O
costing	O
upwards	O
of	O
US	O
$	O
100,000	O
;	O
smaller	O
machines	O
could	O
use	O
the	O
less	O
expensive	O
2260	B-Device
display	O
or	O
later	O
the	O
3270	B-Operating_System
.	O
</s>
<s>
The	O
first	O
disk	B-Device
drives	I-Device
for	O
System/360	B-Application
were	O
IBM	B-Device
2302s	I-Device
and	O
IBM	B-Device
2311s	I-Device
.	O
</s>
<s>
The	O
first	O
drum	O
for	O
System/360	B-Application
was	O
the	O
IBM	O
7320	O
.	O
</s>
<s>
The	O
156KB/second	O
2302	O
was	O
based	O
on	O
the	O
earlier	O
1302	B-Device
and	O
was	O
available	O
as	O
a	O
model	O
3	O
with	O
two	O
112.79MB	O
modules	O
or	O
as	O
a	O
model	O
4	O
with	O
four	O
such	O
modules	O
.	O
</s>
<s>
The	O
2311	O
,	O
with	O
a	O
removable	O
1316	O
disk	B-Operating_System
pack	I-Operating_System
,	O
was	O
based	O
on	O
the	O
IBM	B-Device
1311	I-Device
and	O
had	O
a	O
theoretical	O
capacity	O
of	O
7.2MB	O
,	O
although	O
actual	O
capacity	O
varied	O
with	O
record	O
design	O
.	O
</s>
<s>
(	O
When	O
used	O
with	O
a	O
360/20	B-Device
,	O
the	O
1316	O
pack	O
was	O
formatted	O
into	O
fixed-length	O
270	O
byte	B-Application
sectors	B-Application
,	O
giving	O
a	O
maximum	O
capacity	O
of	O
5.4MB	O
.	O
)	O
</s>
<s>
In	O
1966	O
,	O
the	O
first	O
2314s	B-Device
shipped	O
.	O
</s>
<s>
This	O
device	O
had	O
up	O
to	O
eight	O
usable	O
disk	B-Device
drives	I-Device
with	O
an	O
integral	O
control	O
unit	O
;	O
there	O
were	O
nine	O
drives	O
,	O
but	O
one	O
was	O
reserved	O
as	O
a	O
spare	O
.	O
</s>
<s>
Each	O
drive	O
used	O
a	O
removable	O
2316	O
disk	B-Operating_System
pack	I-Operating_System
with	O
a	O
capacity	O
of	O
nearly	O
28MB	O
.	O
</s>
<s>
The	O
disk	B-Operating_System
packs	I-Operating_System
for	O
the	O
2311	O
and	O
2314	O
were	O
physically	O
large	O
by	O
today	O
's	O
standards	O
—	O
e.g.	O
,	O
the	O
1316	O
disk	B-Operating_System
pack	I-Operating_System
was	O
about	O
in	O
diameter	O
and	O
had	O
six	O
platters	O
stacked	O
on	O
a	O
central	O
spindle	O
.	O
</s>
<s>
These	O
disks	B-Device
were	O
not	O
usually	O
formatted	O
with	O
fixed-sized	O
sectors	B-Application
as	O
are	O
today	O
's	O
hard	O
drives	O
(	O
though	O
this	O
was	O
done	O
with	O
CP/CMS	B-Application
)	O
.	O
</s>
<s>
Rather	O
,	O
most	O
System/360	B-Application
I/O	O
software	O
could	O
customize	O
the	O
length	O
of	O
the	O
data	O
record	O
(	O
variable-length	O
records	O
)	O
,	O
as	O
was	O
the	O
case	O
with	O
magnetic	O
tapes	O
.	O
</s>
<s>
Some	O
of	O
the	O
most	O
powerful	O
early	O
System/360s	B-Application
used	O
high-speed	O
head-per-track	O
drum	B-General_Concept
storage	I-General_Concept
devices	O
.	O
</s>
<s>
The	O
3,500	O
RPM	O
2301	O
,	O
which	O
replaced	O
the	O
7320	O
,	O
was	O
part	O
of	O
the	O
original	O
System/360	B-Application
announcement	O
,	O
with	O
a	O
capacity	O
of	O
4MB	O
.	O
</s>
<s>
These	O
were	O
the	O
only	O
drums	B-General_Concept
announced	O
for	O
System/360	B-Application
and	O
System/370	B-Device
,	O
and	O
their	O
niche	O
was	O
later	O
filled	O
by	O
fixed-head	O
disks	B-Device
.	O
</s>
<s>
Fixed	O
head	O
disks	B-Device
and	O
drums	B-General_Concept
were	O
particularly	O
effective	O
as	O
paging	O
devices	O
on	O
the	O
early	O
virtual	B-Architecture
memory	I-Architecture
systems	O
.	O
</s>
<s>
The	O
2305	O
,	O
although	O
often	O
called	O
a	O
"	O
drum	O
"	O
was	O
actually	O
a	O
head-per-track	O
disk	B-Device
device	O
,	O
with	O
12	O
recording	O
surfaces	O
and	O
a	O
data	O
transfer	O
rate	O
up	O
to	O
3MB	O
per	O
second	O
.	O
</s>
<s>
Rarely	O
seen	O
was	O
the	O
IBM	B-Device
2321	I-Device
Data	I-Device
Cell	I-Device
,	O
a	O
mechanically	O
complex	O
device	O
that	O
contained	O
multiple	O
magnetic	O
strips	O
to	O
hold	O
data	O
;	O
strips	O
could	O
be	O
randomly	O
accessed	O
,	O
placed	O
upon	O
a	O
cylinder-shaped	O
drum	O
for	O
read/write	O
operations	O
;	O
then	O
returned	O
to	O
an	O
internal	O
storage	O
cartridge	O
.	O
</s>
<s>
The	O
IBM	O
Data	B-Device
Cell	I-Device
[	O
noodle	O
picker ]	O
was	O
among	O
several	O
IBM	O
trademarked	O
"	O
speedy	O
"	O
mass	O
online	O
direct-access	O
storage	O
peripherals	O
(	O
reincarnated	O
in	O
recent	O
years	O
as	O
"	O
virtual	O
tape	O
"	O
and	O
automated	O
tape	O
librarian	O
peripherals	O
)	O
.	O
</s>
<s>
The	O
2321	O
file	O
had	O
a	O
capacity	O
of	O
400MB	O
,	O
at	O
the	O
time	O
when	O
the	O
2311	O
disk	B-Device
drive	I-Device
only	O
had	O
7.2MB	O
.	O
</s>
<s>
The	O
IBM	O
Data	B-Device
Cell	I-Device
was	O
proposed	O
to	O
fill	O
cost/capacity/speed	O
gap	O
between	O
magnetic	O
tapes	O
—	O
which	O
had	O
high	O
capacity	O
with	O
relatively	O
low	O
cost	O
per	O
stored	O
byte	B-Application
—	O
and	O
disks	B-Device
,	O
which	O
had	O
higher	O
expense	O
per	O
byte	B-Application
.	O
</s>
<s>
The	O
Model	B-Device
44	I-Device
was	O
unique	O
in	O
offering	O
an	O
integrated	O
single-disk	O
drive	O
as	O
a	O
standard	O
feature	O
.	O
</s>
<s>
This	O
drive	O
used	O
the	O
2315	O
"	O
ramkit	O
"	O
cartridge	O
and	O
provided	O
1,171,200	O
bytes	B-Application
of	O
storage	O
.	O
</s>
<s>
With	O
System/360	B-Application
,	O
IBM	O
switched	O
from	O
IBM	B-Device
7-track	I-Device
to	O
9-track	B-Device
tape	I-Device
format	O
.	O
</s>
<s>
Some	O
2400-series	O
drives	O
could	O
be	O
purchased	O
that	O
read	O
and	O
wrote	O
7-track	B-Device
tapes	I-Device
for	O
compatibility	O
with	O
the	O
older	O
IBM	B-Device
729	I-Device
tape	O
drives	O
.	O
</s>
<s>
Punched	B-Architecture
card	I-Architecture
devices	O
included	O
the	O
2501	O
card	B-Architecture
reader	I-Architecture
and	O
the	O
2540	O
card	B-Architecture
reader	I-Architecture
punch	O
.	O
</s>
<s>
Virtually	O
every	O
System/360	B-Application
had	O
a	O
2540	O
.	O
</s>
<s>
The	O
2560	O
MFCM	O
(	O
"	O
Multi-Function	O
Card	O
Machine	O
"	O
)	O
reader/sorter/punch	O
,	O
listed	O
above	O
,	O
was	O
for	O
the	O
Model	B-Device
20	I-Device
only	O
.	O
</s>
<s>
Line	O
printers	O
were	O
the	O
IBM	B-Device
1403	I-Device
and	O
the	O
slower	O
IBM	B-Device
1443	I-Device
.	O
</s>
<s>
The	O
1054	O
(	O
reader	O
)	O
and	O
1055	O
(	O
punch	O
)	O
,	O
which	O
were	O
carried	O
forward	O
(	O
like	O
the	O
1052	O
console	B-Device
typewriter	O
)	O
from	O
the	O
IBM	B-Device
1050	I-Device
Teleprocessing	O
System	O
.	O
</s>
<s>
Optical	B-Application
character	I-Application
recognition	I-Application
(	O
OCR	O
)	O
devices	O
1287	O
and	O
later	O
the	O
1288	O
were	O
available	O
on	O
the	O
360	O
's	O
.	O
</s>
<s>
Magnetic	O
ink	O
character	B-Application
recognition	I-Application
(	O
MICR	O
)	O
was	O
provided	O
by	O
the	O
IBM	O
1412	O
and	O
1419	O
cheque	O
sorters	O
,	O
with	O
magnetic	O
ink	O
printing	O
(	O
for	O
cheque	O
books	O
)	O
on	O
1445	O
printers	O
(	O
a	O
modified	O
1443	O
that	O
used	O
an	O
MICR	O
ribbon	O
)	O
.	O
</s>
<s>
Despite	O
having	O
been	O
sold	O
or	O
leased	O
in	O
very	O
large	O
numbers	O
for	O
a	O
mainframe	B-Architecture
system	O
of	O
its	O
era	O
,	O
only	O
a	O
few	O
of	O
System/360	B-Application
computers	O
remain	O
—	O
mainly	O
as	O
non-operating	O
property	O
of	O
museums	O
or	O
collectors	O
.	O
</s>
<s>
The	O
Computer	O
History	O
Museum	O
in	O
Mountain	O
View	O
,	O
California	O
,	O
has	O
a	O
non-working	O
Model	B-Device
30	I-Device
on	O
display	O
,	O
as	O
do	O
the	O
Museum	O
of	O
Transport	O
and	O
Technology	O
in	O
Auckland	O
,	O
New	O
Zealand	O
,	O
and	O
the	O
Vienna	O
University	O
of	O
Technology	O
in	O
Austria	O
.	O
</s>
<s>
The	O
University	O
of	O
Western	O
Australia	O
Computer	O
Club	O
has	O
a	O
complete	O
Model	B-Device
40	I-Device
in	O
storage	O
.	O
</s>
<s>
The	O
KCG	O
Computer	O
Museum	O
of	O
Kyoto	O
Computer	O
Gakuin	O
,	O
Japan	O
's	O
first	O
computer	O
school	O
in	O
town	O
,	O
has	O
an	O
IBM	B-Device
System/360	I-Device
Model	I-Device
40	I-Device
on	O
display	O
.	O
</s>
<s>
Two	O
IBM	B-Device
System/360	I-Device
Model	I-Device
20	I-Device
processors	O
along	O
with	O
numerous	O
peripherals	O
(	O
forming	O
two	O
complete	O
systems	O
)	O
located	O
in	O
Nuremberg	O
,	O
Germany	O
,	O
were	O
purchased	O
on	O
eBay	B-Application
in	O
April/May	O
2019	O
for	O
€	O
3,710	O
by	O
two	O
UK	O
enthusiasts	O
,	O
Adam	O
Bradley	O
and	O
Chris	O
Blackburn	O
,	O
who	O
,	O
over	O
the	O
course	O
of	O
some	O
months	O
,	O
moved	O
the	O
machine	O
to	O
Creslow	O
Park	O
in	O
Buckinghamshire	O
,	O
United	O
Kingdom	O
.	O
</s>
<s>
The	O
Living	O
Computers	O
:	O
Museum	O
+	O
Labs	O
has	O
a	O
360	O
model	B-Device
30	I-Device
.	O
</s>
<s>
A	O
running	O
list	O
of	O
remaining	O
System/360s	B-Application
that	O
are	O
more	O
than	O
just	O
'	O
front	O
panels	O
 '	O
can	O
be	O
found	O
at	O
.	O
</s>
<s>
This	O
gallery	O
shows	O
the	O
operator	O
's	O
console	B-Device
,	O
with	O
register	B-General_Concept
value	I-General_Concept
lamps	O
,	O
toggle	O
switches	O
(	O
middle	O
of	O
pictures	O
)	O
,	O
and	O
"	O
emergency	O
pull	O
"	O
switch	O
(	O
upper	O
right	O
of	O
pictures	O
)	O
of	O
the	O
various	O
models	O
.	O
</s>
