<s>
The	O
RCA	B-Device
Spectra	I-Device
70	I-Device
was	O
a	O
line	O
of	O
electronic	B-Application
data	I-Application
processing	I-Application
(	O
EDP	O
)	O
equipment	O
manufactured	O
by	O
the	O
Radio	O
Corporation	O
of	O
America	O
’s	O
computer	O
division	O
beginning	O
in	O
April	O
1965	O
.	O
</s>
<s>
The	O
Spectra	B-Device
70	I-Device
line	O
included	O
several	O
CPU	B-Device
models	O
,	O
various	O
configurations	O
of	O
core	O
memory	O
,	O
mass-storage	B-Device
devices	I-Device
,	O
terminal	B-General_Concept
equipment	O
,	O
and	O
a	O
variety	O
of	O
specialized	O
interface	O
equipment	O
.	O
</s>
<s>
The	O
system	O
architecture	O
and	O
instruction-set	O
were	O
largely	O
compatible	O
with	O
the	O
non-privileged	O
instruction-set	O
of	O
the	O
IBM	B-Application
System/360	I-Application
,	O
including	O
use	O
of	O
the	O
EBCDIC	B-Language
character	O
set	O
.	O
</s>
<s>
While	O
this	O
degree	O
of	O
compatibility	O
made	O
some	O
interchange	O
of	O
programs	O
and	O
data	O
possible	O
,	O
differences	O
in	O
the	O
operating	B-General_Concept
system	I-General_Concept
software	O
precluded	O
transparent	O
movement	O
of	O
programs	O
between	O
the	O
two	O
systems	O
.	O
</s>
<s>
Competition	O
in	O
the	O
mainframe	B-Architecture
market	O
was	O
fierce	O
,	O
and	O
in	O
1971	O
the	O
company	O
sold	O
the	O
computer	O
division	O
and	O
the	O
Spectra	B-Device
70	I-Device
line	O
to	O
Sperry	O
Rand	O
,	O
taking	O
a	O
huge	O
write	O
down	O
in	O
the	O
process	O
.	O
</s>
<s>
Five	O
models	O
of	O
the	O
Spectra	B-Device
70	I-Device
CPU	B-Device
were	O
announced	O
around	O
1965	O
,	O
ranging	O
from	O
a	O
small	O
system	O
(	O
70/15	O
)	O
to	O
the	O
large	O
scale	O
(	O
70/55	O
)	O
.	O
</s>
<s>
The	O
systems	O
were	O
upward-compatible	B-General_Concept
,	O
allowing	O
programs	O
written	O
for	O
a	O
smaller	O
model	O
to	O
run	O
on	O
any	O
larger	O
machine	O
in	O
the	O
series	O
.	O
</s>
<s>
Larger	O
machines	O
in	O
the	O
series	O
were	O
also	O
faster	O
,	O
with	O
memory	O
access	B-General_Concept
times	I-General_Concept
ranging	O
from	O
two	O
microseconds	O
in	O
the	O
70/15	O
to	O
0.84	O
microseconds	O
in	O
the	O
70/55	O
.	O
</s>
<s>
Memory	O
capacities	O
ranged	O
from	O
a	O
minimum	O
of	O
4,096	O
bytes	B-Application
(	O
4KB	O
)	O
in	O
the	O
70/15	O
to	O
a	O
maximum	O
of	O
524,288	O
bytes	B-Application
(	O
512KB	O
)	O
in	O
the	O
70/55	O
.	O
</s>
<s>
All	O
used	O
the	O
Extended	B-Language
Binary	I-Language
Coded	I-Language
Decimal	I-Language
Interchange	I-Language
Code	I-Language
(	O
EBCDIC	B-Language
)	O
of	O
eight	O
bits	O
plus	O
parity	O
for	O
internal	O
data	O
representation	O
.	O
</s>
<s>
The	O
use	O
of	O
a	O
standard	O
electrical	O
interface	O
allowed	O
the	O
same	O
peripherals	O
to	O
be	O
used	O
with	O
any	O
CPU	B-Device
model	O
in	O
the	O
series	O
.	O
</s>
<s>
Like	O
the	O
IBM	B-Application
360	I-Application
,	O
two	O
types	O
of	O
channel	O
were	O
available	O
(	O
on	O
all	O
but	O
the	O
70/15	O
)	O
:	O
selector	O
channels	O
which	O
could	O
address	O
up	O
to	O
256	O
devices	O
(	O
one	O
at	O
a	O
time	O
)	O
,	O
and	O
multiplexer	B-Protocol
channels	O
(	O
not	O
on	O
the	O
70/15	O
)	O
which	O
could	O
simultaneously	O
address	O
up	O
to	O
256	O
channels	O
by	O
time-sharing	B-General_Concept
the	O
channel	O
.	O
</s>
<s>
The	O
full	O
instruction	B-General_Concept
set	I-General_Concept
comprised	O
144	O
instructions	O
,	O
including	O
optional	O
floating-point	B-General_Concept
.	O
</s>
<s>
Floating-point	B-General_Concept
instructions	O
were	O
not	O
available	O
on	O
the	O
70/15	O
and	O
70/25	O
.	O
</s>
<s>
These	O
systems	O
all	O
ran	O
RCA	O
's	O
real-memory	O
operating	B-General_Concept
systems	I-General_Concept
,	O
DOS	O
and	O
TDOS	O
.	O
</s>
<s>
The	O
70/45	O
could	O
also	O
run	O
a	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
,	O
The	O
RCA	O
70/45	O
Basic	O
Time	B-General_Concept
Sharing	I-General_Concept
System	O
(	O
BTSS	O
)	O
,	O
supporting	O
up	O
to	O
16	O
users	O
.	O
</s>
<s>
The	O
systems	O
that	O
supported	O
virtual	B-Architecture
memory	I-Architecture
,	O
the	O
Spectra	O
70/46	O
and	O
70/61	O
and	O
the	O
later	O
RCA	O
3	O
and	O
7	O
,	O
could	O
also	O
run	O
the	O
RCA	O
's	O
Virtual	B-Operating_System
Memory	I-Operating_System
Operating	I-Operating_System
System	I-Operating_System
(	O
VMOS	O
)	O
.	O
</s>
<s>
VMOS	O
was	O
originally	O
named	O
TSOS	O
(	O
Time	B-Operating_System
Sharing	I-Operating_System
Operating	I-Operating_System
System	I-Operating_System
)	O
,	O
but	O
was	O
renamed	O
to	O
expand	O
the	O
market	O
for	O
the	O
system	O
beyond	O
time-sharing	B-General_Concept
.	O
</s>
<s>
TSOS	O
was	O
the	O
first	O
mainframe	B-Architecture
,	O
demand	B-General_Concept
paged	I-General_Concept
,	O
virtual	B-Operating_System
memory	I-Operating_System
operating	I-Operating_System
system	I-Operating_System
on	O
the	O
market	O
.	O
</s>
<s>
The	O
Spectra	O
series	O
was	O
later	O
supplemented	O
by	O
the	O
RCA	O
Series	O
(	O
RCA	O
2	O
,	O
3	O
,	O
6	O
,	O
7	O
—	O
later	O
renamed	O
the	O
70/2	O
,	O
70/3	O
,	O
70/6	O
,	O
and	O
70/7	O
,	O
which	O
competed	O
against	O
the	O
IBM	B-Device
System/370	I-Device
.	O
</s>
<s>
The	O
RCA	O
2	O
and	O
6	O
ran	O
the	O
real-memory	O
batch-oriented	B-General_Concept
OS/70	O
operating	B-General_Concept
system	I-General_Concept
,	O
while	O
the	O
RCA	O
3	O
and	O
7	O
ran	O
VMOS	O
.	O
</s>
<s>
Some	O
English	B-Device
Electric	I-Device
System	I-Device
4	I-Device
mainframes	B-Architecture
were	O
rebadged	O
Spectra	B-Device
70	I-Device
machines	O
;	O
others	O
were	O
English	O
Electric-designed	O
clones	O
of	O
the	O
RCA	B-Device
Spectra	I-Device
70	I-Device
clones	O
of	O
the	O
IBM	B-Application
System/360	I-Application
range	O
.	O
</s>
<s>
The	O
RCA	O
Model	O
70/15	O
(	O
1965	O
)	O
was	O
a	O
discrete	O
small-scale	O
processor	B-General_Concept
that	O
could	O
still	O
support	O
a	O
variety	O
of	O
applications	B-Application
.	O
</s>
<s>
It	O
implemented	O
a	O
small	O
subset	O
of	O
25	O
instructions	O
of	O
the	O
full	O
Spectra	B-Device
70	I-Device
architecture	O
,	O
and	O
was	O
not	O
downward	B-General_Concept
compatible	I-General_Concept
with	O
the	O
rest	O
of	O
the	O
range	O
.	O
</s>
<s>
Also	O
,	O
the	O
limited	O
memory	O
size	O
available	O
"	O
obviates	O
the	O
need	O
for	O
a	O
base	O
address	O
in	O
that	O
the	O
displacement	O
has	O
the	O
necessary	O
addressing	O
range	O
by	O
the	O
addition	O
of	O
a	O
high-order	O
bit	O
to	O
permit	O
addressing	O
of	O
up	O
to	O
8,192	O
bytes.	O
"	O
</s>
<s>
In	O
this	O
respect	O
it	O
was	O
similar	O
to	O
the	O
IBM	B-Device
System/360	I-Device
Model	I-Device
20	I-Device
.	O
</s>
<s>
Two	O
memory	O
configurations	O
for	O
the	O
70/15	O
were	O
available	O
:	O
either	O
4,096	O
bytes	B-Application
or	O
8,192	O
bytes	B-Application
of	O
core	O
memory	O
.	O
</s>
<s>
The	O
memory	O
cycle	O
time	O
for	O
a	O
70/15	O
was	O
2	O
microseconds	O
per	O
byte	B-Application
of	O
information	O
.	O
</s>
<s>
The	O
70/15	O
was	O
often	O
used	O
as	O
a	O
satellite	O
processor	B-General_Concept
for	O
larger	O
systems	O
or	O
used	O
as	O
an	O
intelligent	O
terminal	B-General_Concept
for	O
remote	O
job	O
entry	O
.	O
</s>
<s>
Typical	O
applications	B-Application
of	O
a	O
satellite	O
processor	B-General_Concept
would	O
include	O
card-to-tape	O
conversion	O
,	O
card/tape	O
-to-printer	O
report	O
generation	O
,	O
tape-to-card	O
punching	O
,	O
input	O
pre-processing	O
and	O
verification	O
,	O
or	O
tab-shop	O
tasks	O
like	O
file	O
sorting	B-Algorithm
,	O
merge	B-Algorithm
,	O
and	O
data	O
selection	O
.	O
</s>
<s>
Software	O
for	O
this	O
model	O
did	O
not	O
include	O
an	O
operating	B-General_Concept
system	I-General_Concept
—	O
the	O
RCA	O
70/15	O
Programming	O
System	O
consisted	O
of	O
an	O
"	O
Assembly	O
System	O
,	O
Loader	O
Routines	O
,	O
Input-Output	B-Application
Control	I-Application
,	O
Test	O
Routines	O
,	O
Utility	B-Application
Routines	I-Application
,	O
Communication	O
Control	O
,	O
System	O
Maintenance	O
Routines	O
,	O
Report	B-Language
Program	I-Language
Generator	I-Language
,	O
and	O
Sort/Merge.	O
"	O
</s>
<s>
Sort/Merge	O
required	O
a	O
system	O
with	O
8KB	O
of	O
memory	O
.	O
</s>
<s>
Programs	O
could	O
be	O
run	O
from	O
punched-cards	B-Architecture
or	O
magnetic	O
tape	O
.	O
</s>
<s>
The	O
RCA	O
Model	O
70/25	O
(	O
1965	O
)	O
was	O
a	O
discrete	O
small-to-medium	O
scale	O
computer	O
system	O
that	O
supported	O
a	O
wider	O
variety	O
of	O
applications	B-Application
,	O
including	O
use	O
as	O
a	O
free	O
standing	O
system	O
.	O
</s>
<s>
In	O
large	O
installations	O
,	O
the	O
70/25	O
might	O
also	O
be	O
used	O
as	O
a	O
subsystem	O
in	O
a	O
multi-processor	B-Operating_System
complex	O
.	O
</s>
<s>
Equipped	O
with	O
selector	O
channels	O
and	O
a	O
multiplexer	B-Protocol
channel	O
,	O
the	O
70/25	O
could	O
concurrently	O
operate	O
eight	O
low-speed	O
devices	O
in	O
addition	O
to	O
eight	O
high-speed	O
devices	O
.	O
</s>
<s>
Memory	O
capacities	O
for	O
the	O
70/25	O
ranged	O
from	O
a	O
minimum	O
of	O
16,384	O
bytes	B-Application
to	O
a	O
maximum	O
of	O
65,536	O
bytes	B-Application
.	O
</s>
<s>
The	O
memory	O
cycle	O
time	O
was	O
1.5	O
microseconds	O
to	O
access	O
one	O
8	O
bit	O
byte	B-Application
.	O
</s>
<s>
Unlike	O
the	O
Model	O
70/45	O
and	O
70/55	O
it	O
did	O
not	O
offer	O
the	O
option	O
of	O
a	O
floating	B-General_Concept
point	I-General_Concept
processor	I-General_Concept
.	O
</s>
<s>
The	O
maximum	O
memory	O
was	O
limited	O
to	O
32,768	O
bytes	B-Application
from	O
two	O
16,384	O
byte	B-Application
core	O
memories	O
.	O
</s>
<s>
The	O
RCA	O
Model	O
70/45	O
(	O
1966	O
)	O
was	O
a	O
medium	O
scale	O
processor	B-General_Concept
of	O
relatively	O
good	O
performance	O
for	O
its	O
time	O
.	O
</s>
<s>
A	O
floating-point	B-General_Concept
processor	I-General_Concept
was	O
available	O
as	O
an	O
option	O
and	O
the	O
70/45	O
was	O
considered	O
suitable	O
for	O
commercial	O
,	O
scientific	O
,	O
communications	O
,	O
and	O
real-time	O
applications	B-Application
.	O
</s>
<s>
With	O
a	O
communications	O
multiplexer	B-Protocol
,	O
the	O
70/45	O
could	O
accommodate	O
up	O
to	O
256	O
communication	O
lines	O
for	O
interactive	O
use	O
as	O
well	O
as	O
batch	B-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
Memory	O
capacity	O
for	O
the	O
70/45	O
ranged	O
from	O
a	O
minimum	O
of	O
16,384	O
bytes	B-Application
(	O
16KB	O
)	O
to	O
262,144	O
bytes	B-Application
(	O
256KB	O
)	O
.	O
</s>
<s>
The	O
memory	O
cycle	O
time	O
was	O
1.44	O
microseconds	O
to	O
access	O
two	O
bytes	B-Application
(	O
one	O
half	O
word	O
)	O
of	O
information	O
.	O
</s>
<s>
The	O
RCA	O
Model	O
70/46	O
(	O
1967	O
)	O
is	O
a	O
modified	O
version	O
of	O
the	O
70/45	O
with	O
an	O
added	O
virtual	B-Architecture
memory	I-Architecture
capability	O
.	O
</s>
<s>
Advertisements	O
for	O
this	O
computer	O
as	O
a	O
timesharing	B-General_Concept
machine	O
referred	O
to	O
it	O
as	O
the	O
Octoputer	O
.	O
</s>
<s>
Programs	O
can	O
run	O
in	O
either	O
70/45	O
mode	O
—	O
without	O
virtual	B-Architecture
memory	I-Architecture
—	O
or	O
in	O
70/46	O
mode	O
with	O
virtual	B-Architecture
memory	I-Architecture
enabled	O
.	O
</s>
<s>
Pages	O
can	O
be	O
specified	O
to	O
be	O
either	O
2048	O
or	O
4096	O
bytes	B-Application
in	O
length	O
,	O
depending	O
on	O
program	O
requirements	O
,	O
however	O
2048	O
byte	B-Application
pages	O
occupy	O
the	O
lower	O
half	O
of	O
a	O
page	O
frame	O
in	O
memory	O
.	O
</s>
<s>
Virtual	B-Architecture
memory	I-Architecture
is	O
divided	O
into	O
segments	O
of	O
64	O
pages	O
indicated	O
by	O
bits	O
1-5	O
of	O
a	O
virtual	O
address	O
.	O
</s>
<s>
Although	O
the	O
Instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
defines	O
up	O
to	O
32	O
segments	O
,	O
only	O
eight	O
are	O
used	O
in	O
the	O
70/46	O
.	O
</s>
<s>
With	O
4KB	O
pages	O
,	O
segments	O
are	O
256KB	O
in	O
length	O
,	O
and	O
total	O
virtual	B-Architecture
memory	I-Architecture
size	O
is	O
up	O
to	O
2MB	O
.	O
</s>
<s>
The	O
RCA	O
Model	O
70/55	O
(	O
1966	O
)	O
was	O
a	O
medium-to-large	O
scale	O
processor	B-General_Concept
with	O
excellent	O
processor	B-General_Concept
characteristics	O
well	O
suited	O
to	O
both	O
scientific	O
and	O
large-scale	O
commercial	O
processing	O
.	O
</s>
<s>
Memory	O
capacity	O
for	O
the	O
70/55	O
ranged	O
from	O
65,536	O
bytes	B-Application
(	O
64KB	O
)	O
of	O
core	O
memory	O
to	O
524,288	O
bytes	B-Application
(	O
512KB	O
)	O
.	O
</s>
<s>
The	O
memory	O
cycle	O
time	O
was	O
0.84	O
microseconds	O
to	O
access	O
four	O
bytes	B-Application
of	O
information	O
.	O
</s>
<s>
The	O
RCA	O
Model	O
70/60	O
was	O
a	O
later	O
addition	O
to	O
the	O
Spectra	B-Device
70	I-Device
series	O
,	O
having	O
been	O
announced	O
in	O
1969	O
.	O
</s>
<s>
Although	O
these	O
computers	O
were	O
fast	O
and	O
reliable	O
they	O
came	O
too	O
late	O
to	O
impact	O
the	O
lead	O
of	O
the	O
IBM	B-Application
360	I-Application
product	O
line	O
.	O
</s>
<s>
Input-output	O
devices	O
on	O
the	O
Spectra	B-Device
70	I-Device
series	O
were	O
specifically	O
designed	O
to	O
interface	O
with	O
all	O
models	O
of	O
the	O
Spectra	O
processor	B-General_Concept
using	O
the	O
RCA	O
Standard	O
Interface	O
.	O
</s>
<s>
In	O
purely	O
numeric	B-Algorithm
mode	O
,	O
the	O
tape	O
reading	O
and	O
writing	O
was	O
performed	O
at	O
240,000	O
digits	O
per	O
second	O
.	O
</s>
<s>
Direct	B-Application
access	I-Application
storage	I-Application
was	O
available	O
in	O
the	O
form	O
of	O
a	O
high-speed	O
70/565	O
Drum	B-General_Concept
Memory	I-General_Concept
Unit	O
with	O
a	O
capacity	O
of	O
1	O
MB	O
and	O
an	O
average	O
access	B-General_Concept
time	I-General_Concept
of	O
8.6	O
milliseconds	O
,	O
a	O
70/564	O
Disc	B-Device
Storage	O
Unit	O
with	O
an	O
interchangeable	O
7.25	O
MB	O
disc-pack	B-Operating_System
and	O
a	O
data	O
interchange	O
rate	O
of	O
156	O
kbyte/s	O
,	O
and	O
a	O
70/568	O
-11	O
Mass	B-Device
Storage	I-Device
Unit	O
with	O
8	O
interchangeable	O
67	O
MB	O
magazines	O
.	O
</s>
<s>
The	O
Videoscan	O
Document	O
Reader	O
was	O
an	O
optical	B-Application
character	I-Application
recognition	I-Application
scanner	B-Application
with	O
a	O
speed	O
of	O
1,300	O
documents	O
per	O
minute	O
.	O
</s>
