<s>
Nord-10	B-Device
was	O
a	O
medium-sized	O
general-purpose	O
16-bit	B-Device
minicomputer	B-Architecture
designed	O
for	O
multilingual	O
time-sharing	B-General_Concept
applications	O
and	O
for	O
real-time	B-General_Concept
multi-program	O
systems	O
,	O
produced	O
by	O
Norsk	O
Data	O
.	O
</s>
<s>
The	O
later	O
follow	O
up	O
model	O
,	O
Nord-10/S	B-Device
,	O
introduced	O
in	O
1975	O
,	O
introduced	O
CPU	B-General_Concept
cache	I-General_Concept
,	O
paging	B-Architecture
,	O
and	O
other	O
miscellaneous	O
improvements	O
.	O
</s>
<s>
The	O
CPU	O
additionally	O
contained	O
instructions	O
,	O
operator	O
communication	O
,	O
bootstrap	O
loaders	O
,	O
and	O
hardware	O
test	O
programs	O
,	O
that	O
were	O
implemented	O
in	O
a	O
1K	O
read-only	B-Device
memory	I-Device
.	O
</s>
<s>
Nord-10	B-Device
had	O
a	O
memory	O
management	O
system	O
with	O
hardware	O
paging	B-Architecture
extending	O
the	O
memory	O
size	O
from	O
64	O
to	O
256K	O
16-bit	B-Device
words	O
and	O
two	O
independent	O
protecting	O
systems	O
,	O
one	O
acting	O
on	O
each	O
page	O
and	O
one	O
on	O
the	O
mode	O
of	O
instructions	O
.	O
</s>
<s>
The	O
interrupt	B-Application
system	O
had	O
16	O
program	O
levels	O
in	O
hardware	O
,	O
each	O
with	O
its	O
own	O
set	O
of	O
general-purpose	O
registers	O
.	O
</s>
<s>
Note	O
:	O
Much	O
of	O
the	O
following	O
information	O
is	O
taken	O
from	O
a	O
document	O
written	O
by	O
Norsk	O
Data	O
introducing	O
the	O
Nord-10	B-Device
.	O
</s>
<s>
Some	O
information	O
,	O
particularly	O
about	O
the	O
memory	O
system	O
,	O
may	O
be	O
inaccurate	O
for	O
the	O
later	O
Nord-10/S	B-Device
.	O
</s>
<s>
The	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
consisted	O
of	O
a	O
total	O
24	O
printed	O
circuit	O
boards	O
.	O
</s>
<s>
The	O
last	O
eight	O
positions	O
in	O
the	O
rack	O
were	O
used	O
for	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
devices	O
operated	O
by	O
program	O
control	O
,	O
such	O
as	O
the	O
console	O
teleprinter	O
(	O
teletype	O
)	O
,	O
paper	O
punched	O
tape	O
and	O
punched	B-Architecture
card	I-Architecture
reader	O
and	O
punch	O
,	O
line	O
printer	O
,	O
display	O
,	O
operator	O
's	O
panel	O
,	O
and	O
a	O
real-time	B-General_Concept
clock	O
.	O
</s>
<s>
The	O
Nord-10	B-Device
had	O
160	O
processor	B-General_Concept
registers	I-General_Concept
,	O
of	O
which	O
128	O
were	O
available	O
to	O
programs	O
,	O
eight	O
on	O
each	O
of	O
the	O
16	O
program	O
levels	O
.	O
</s>
<s>
Six	O
of	O
those	O
registers	O
were	O
general	O
registers	O
,	O
one	O
was	O
the	O
program	B-General_Concept
counter	I-General_Concept
,	O
and	O
the	O
other	O
contained	O
status	O
information	O
.	O
</s>
<s>
Floating	B-Algorithm
point	I-Algorithm
arithmetic	I-Algorithm
operations	O
were	O
standard	O
.	O
</s>
<s>
The	O
instructions	O
could	O
operate	O
on	O
five	O
different	O
formats	O
,	O
a	O
bit	O
,	O
an	O
8-bit	O
byte	B-Application
,	O
16-bit	B-Device
words	O
,	O
32-bit	O
double	O
words	O
,	O
and	O
48-bit	O
floating	B-Algorithm
point	I-Algorithm
words	O
.	O
</s>
<s>
The	O
random-access	B-Architecture
memory	I-Architecture
system	O
of	O
the	O
first	O
Nord-10s	B-Device
were	O
built	O
up	O
of	O
8K	O
16-bit	B-Device
modules	O
housed	O
in	O
a	O
special	O
memory	O
rack	O
.	O
</s>
<s>
One	O
19-inch	B-Application
rack	I-Application
could	O
hold	O
up	O
to	O
eight	O
8K	O
modules	O
.	O
</s>
<s>
It	O
was	O
possible	O
to	O
extend	O
the	O
Nord-10	B-Device
'	O
s	O
physical	B-General_Concept
address	I-General_Concept
space	O
beyond	O
64K	O
up	O
to	O
a	O
maximum	O
of	O
256K	O
16-bit	B-Device
words	O
.	O
</s>
<s>
The	O
paging	B-Architecture
system	O
translated	O
a	O
16-bit	B-Device
virtual	B-General_Concept
address	I-General_Concept
into	O
an	O
18-bit	O
physical	B-General_Concept
address	I-General_Concept
.	O
</s>
<s>
The	O
hardware	O
paging	B-Architecture
system	O
made	O
it	O
possible	O
for	O
one	O
user	O
to	O
write	O
programs	O
up	O
to	O
64K	O
(	O
virtual	O
memory	O
)	O
,	O
and	O
only	O
parts	O
of	O
the	O
program	O
to	O
be	O
present	O
in	O
physical	O
memory	O
at	O
any	O
time	O
(	O
using	O
dynamic	O
memory	O
allocation	O
)	O
.	O
</s>
<s>
The	O
paging	B-Architecture
system	O
divided	O
memory	O
into	O
1K	O
pages	O
.	O
</s>
<s>
The	O
calculation	O
of	O
a	O
physical	B-General_Concept
address	I-General_Concept
resulted	O
in	O
no	O
appreciable	O
delay	O
in	O
the	O
effective	O
memory	O
cycle	O
time	O
.	O
</s>
<s>
The	O
Nord-10	B-Device
had	O
two	O
independent	O
protection	O
systems	O
.	O
</s>
<s>
In	O
addition	O
,	O
there	O
was	O
a	O
system	O
which	O
divided	O
the	O
pages	O
into	O
four	O
different	O
categories	O
,	O
called	O
rings	B-Operating_System
.	O
</s>
<s>
The	O
rings	B-Operating_System
had	O
a	O
priority	O
from	O
0	O
to	O
3	O
.	O
</s>
<s>
Programs	O
which	O
ran	O
on	O
rings	B-Operating_System
2	O
and	O
3	O
could	O
use	O
the	O
whole	O
Nord-10	B-Device
instruction	O
set	O
,	O
while	O
programs	O
on	O
rings	B-Operating_System
0	O
and	O
1	O
only	O
had	O
a	O
limited	O
instruction	O
set	O
available	O
.	O
</s>
<s>
The	O
different	O
rings	B-Operating_System
were	O
displayed	O
on	O
the	O
operator	O
's	O
panel	O
.	O
</s>
<s>
For	O
example	O
,	O
ring	B-Operating_System
0	I-Operating_System
(	O
User	O
)	O
may	O
have	O
held	O
a	O
user	O
program	O
,	O
while	O
compilers	O
and	O
assemblers	O
ran	O
in	O
ring	B-Operating_System
1	I-Operating_System
(	O
Protected	O
User	O
)	O
.	O
</s>
<s>
The	O
bulk	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
could	O
run	O
in	O
ring	B-Operating_System
2	I-Operating_System
(	O
System	O
)	O
,	O
and	O
the	O
kernel	O
in	O
ring	B-Operating_System
3	I-Operating_System
(	O
Protected	O
System	O
)	O
.	O
</s>
<s>
If	O
one	O
attempted	O
to	O
execute	O
privileged	O
instructions	O
in	O
ring	B-Operating_System
0	I-Operating_System
or	O
1	O
,	O
or	O
attempts	O
were	O
made	O
to	O
accessed	O
a	O
protected	O
page	O
,	O
a	O
hardware	O
status	O
interrupt	B-Application
would	O
automatically	O
be	O
generated	O
on	O
program	O
level	O
14	O
indicating	O
the	O
error	O
.	O
</s>
<s>
The	O
NORD-10	B-Device
was	O
equipped	O
with	O
a	O
common	O
bus	B-General_Concept
system	O
for	O
all	O
external	O
peripheral	B-Device
devices	I-Device
.	O
</s>
<s>
The	O
bus	B-General_Concept
system	O
was	O
divided	O
into	O
groups	O
,	O
and	O
a	O
great	O
deal	O
of	O
effort	O
had	O
been	O
made	O
to	O
ensure	O
that	O
no	O
device	O
would	O
be	O
able	O
to	O
jam	O
the	O
bus	B-General_Concept
system	O
in	O
the	O
case	O
of	O
malfunction	O
.	O
</s>
<s>
Each	O
group	O
had	O
its	O
own	O
controller	O
which	O
in	O
addition	O
to	O
functioning	O
as	O
an	O
electronic	O
switch	O
for	O
the	O
bus	B-General_Concept
system	O
,	O
could	O
also	O
change	O
priority	O
for	O
the	O
whole	O
group	O
.	O
</s>
<s>
All	O
interconnections	O
between	O
the	O
cards	O
were	O
done	O
with	O
multilayer	O
printed	O
circuit	O
backwiring	B-Architecture
boards	I-Architecture
,	O
and	O
all	O
input/output	B-General_Concept
interface	B-Application
had	O
the	O
same	O
standard	O
form	O
.	O
</s>
<s>
The	O
system	O
could	O
therefore	O
be	O
extended	O
or	O
reconfigured	O
by	O
plugging	O
in	O
new	O
or	O
shifting	O
around	O
the	O
existing	O
interface	B-Application
cards	O
.	O
</s>
<s>
The	O
position	O
of	O
the	O
device	O
interface	B-Application
in	O
the	O
card	O
rack	O
determined	O
the	O
interrupt	B-Operating_System
priority	I-Operating_System
of	O
the	O
device	O
.	O
</s>
<s>
In	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
transfers	O
the	O
device	O
would	O
send	O
a	O
request	O
.	O
</s>
<s>
When	O
two	O
or	O
more	O
devices	O
request	O
a	O
DMA	B-General_Concept
request	I-General_Concept
simultaneously	O
to	O
the	O
CPU	O
had	O
the	O
highest	O
priority	O
.	O
</s>
<s>
This	O
meant	O
that	O
many	O
DMA	O
devices	O
could	O
use	O
the	O
same	O
bus	B-General_Concept
system	O
at	O
the	O
full	O
data	O
transfer	O
rate	O
.	O
</s>
<s>
The	O
transfer	O
was	O
one	O
16-bit	B-Device
word/850	O
nanoseconds	O
,	O
or	O
2.2MB/s	O
.	O
</s>
<s>
The	O
printed	O
backplane	B-Architecture
of	O
the	O
I/O	B-General_Concept
bus	I-General_Concept
was	O
modular	O
in	O
groups	O
of	O
8	O
interface	B-Application
slots	O
.	O
</s>
<s>
Interfaces	B-Application
for	O
mass	B-Device
storages	I-Device
as	O
disk	B-Device
,	O
drum	B-General_Concept
,	O
magnetic	O
tape	O
,	O
etc.	O
,	O
were	O
built	O
with	O
one	O
interface	B-Application
card	O
to	O
be	O
plugged	O
at	O
the	O
appropriate	O
place	O
in	O
the	O
bus	B-General_Concept
system	O
,	O
the	O
remaining	O
control	O
cards	O
(	O
6-7	O
)	O
were	O
placed	O
in	O
one	O
of	O
the	O
backplane	B-Architecture
modules	O
.	O
</s>
<s>
The	O
Nord-10	B-Device
had	O
a	O
multi-program	O
system	O
with	O
16	O
priority	O
program	O
levels	O
.	O
</s>
<s>
Each	O
program	O
level	O
had	O
its	O
own	O
set	O
of	O
registers	O
,	O
including	O
a	O
program	B-General_Concept
counter	I-General_Concept
and	O
a	O
status	B-Device
word	I-Device
.	O
</s>
<s>
The	O
levels	O
running	O
could	O
be	O
shown	O
on	O
the	O
front	B-Device
panel	I-Device
by	O
pressing	O
the	O
button	O
"	O
active	O
levels	O
"	O
.	O
</s>
<s>
Levels	O
10	O
,	O
11	O
,	O
12	O
,	O
and	O
13	O
were	O
reserved	O
for	O
external	B-Device
devices	I-Device
.	O
</s>
<s>
The	O
"	O
ident	O
"	O
instruction	O
determined	O
which	O
device	O
was	O
giving	O
an	O
interrupt	B-Application
.	O
</s>
<s>
The	O
identification	O
of	O
an	O
interrupt	B-Application
took	O
1.7	O
microseconds	O
,	O
including	O
the	O
time	O
taken	O
to	O
enable	O
and	O
disable	O
the	O
registers	O
.	O
</s>
<s>
The	O
Nord-10	B-Device
was	O
delivered	O
with	O
a	O
time-shared	O
system	O
,	O
Nord-TSS	O
,	O
and	O
a	O
real-time	B-General_Concept
multitasking	O
operating	B-General_Concept
system	I-General_Concept
,	O
Sintran	B-Operating_System
III	I-Operating_System
.	O
</s>
<s>
The	O
minimum	O
configuration	O
for	O
Sintran	B-Operating_System
III	I-Operating_System
included	O
a	O
standard	O
Nord-10	B-Device
with	O
8K	O
of	O
magnetic-core	O
memory	O
.	O
</s>
<s>
With	O
NORD-TSS	O
all	O
users	O
could	O
simultaneously	O
run	O
any	O
of	O
the	O
systems	O
Fortran	O
IV	O
,	O
BASIC	O
,	O
MAC	O
Assembler	O
,	O
NODAL	B-Application
,	O
NORD-PL	B-Language
,	O
or	O
QED	B-Application
.	O
</s>
<s>
There	O
are	O
several	O
Nord-10	B-Device
and	O
Nord-10/S	B-Device
systems	O
known	O
to	O
remain	O
,	O
many	O
of	O
which	O
are	O
in	O
near-operational	O
condition	O
,	O
and	O
several	O
are	O
in	O
the	O
care	O
of	O
NODAF	O
.	O
</s>
<s>
Its	O
predecessor	O
was	O
the	O
Nord-1	B-Device
and	O
its	O
successor	O
the	O
Nord-100	B-Device
.	O
</s>
