<s>
The	O
SDS	B-Device
9	I-Device
Series	I-Device
computers	O
are	O
a	O
backward	B-General_Concept
compatible	I-General_Concept
line	O
of	O
transistorized	O
computers	O
produced	O
by	O
Scientific	O
Data	O
Systems	O
in	O
the	O
1960s	O
and	O
1970s	O
.	O
</s>
<s>
This	O
line	O
includes	O
the	O
SDS	B-Device
910	I-Device
,	O
SDS	B-Device
920	I-Device
,	O
SDS	B-Device
925	I-Device
,	O
SDS	B-Device
930	I-Device
,	O
SDS	B-Device
940	I-Device
,	O
and	O
the	O
SDS	O
945	O
.	O
</s>
<s>
The	O
SDS	B-Device
9300	I-Device
is	O
an	O
extension	O
of	O
the	O
9xx	O
architecture	O
.	O
</s>
<s>
The	O
9	O
series	O
was	O
replaced	O
by	O
the	O
SDS	B-Device
Sigma	I-Device
series	I-Device
.	O
</s>
<s>
Fixed	O
point	O
data	O
is	O
24-bits	O
,	O
two	B-General_Concept
's	I-General_Concept
complement	I-General_Concept
,	O
big-endian	O
.	O
</s>
<s>
Floating	B-Algorithm
point	I-Algorithm
is	O
implemented	O
in	O
software	O
using	O
"	O
programmed	O
operators	O
"	O
,	O
except	O
on	O
the	O
SDS	B-Device
9300	I-Device
which	O
has	O
hardware	O
floating	B-Algorithm
point	I-Algorithm
.	O
</s>
<s>
All	O
floating	B-Algorithm
point	I-Algorithm
numbers	I-Algorithm
are	O
stored	O
as	O
48-bit	O
double	O
words	O
.	O
</s>
<s>
Both	O
the	O
exponent	O
and	O
the	O
fraction	O
are	O
stored	O
in	O
big-endian	O
twos-complement	B-General_Concept
format	O
.	O
</s>
<s>
The	O
floating	B-Algorithm
point	I-Algorithm
formats	I-Algorithm
are	O
:	O
</s>
<s>
Two	O
hardware	O
interrupts	B-Application
are	O
standard	O
with	O
up	O
to	O
896	O
more	O
optional	O
.	O
</s>
<s>
The	O
SDS	B-Device
910	I-Device
weighed	O
about	O
.	O
</s>
<s>
The	O
920	O
can	O
have	O
up	O
to	O
1024	O
priority	O
interrupts	B-Application
.	O
</s>
<s>
The	O
priority	O
interrupt	B-Application
system	O
allows	O
2	O
–	O
38	O
input/output	O
interrupts	B-Application
and	O
up	O
to	O
896	O
system	O
interrupts	B-Application
.	O
</s>
<s>
The	O
940	O
accesses	O
memory	O
through	O
a	O
memory	O
map	O
to	O
provide	O
virtual	B-Architecture
memory	I-Architecture
.	O
</s>
<s>
This	O
divides	O
virtual	B-Architecture
memory	I-Architecture
logically	O
into	O
eight	O
blocks	O
of	O
2048	O
words	O
each	O
.	O
</s>
<s>
Rn	O
=	O
0	O
and	O
Pn	O
=	O
1	O
indicates	O
an	O
unassigned	O
block	O
,	O
and	O
any	O
reference	O
causes	O
a	O
trap	B-Application
.	O
</s>
<s>
The	O
MAGPAK	O
9446	O
tape	O
drive	O
subsystem	O
and	O
associated	O
9401	O
tape	O
cartridge	O
was	O
developed	O
by	O
SDS	O
for	O
the	O
SDS	O
900	O
series	O
and	O
announced	O
in	O
May	O
1964	O
Each	O
tape	O
drive	O
unit	O
consists	O
of	O
two	O
independently	O
controlled	O
magnetic	B-Architecture
tape	I-Architecture
drives	I-Architecture
mounted	O
on	O
a	O
standard	O
10½-inch	O
by	O
19-inch	O
panel	O
.	O
</s>
<s>
MONARCH	O
is	O
a	O
single-task	O
batch	B-General_Concept
operating	O
system	O
.	O
</s>
<s>
Originally	O
resident	O
on	O
magnetic	B-Architecture
tape	I-Architecture
,	O
later	O
versions	O
can	O
reside	O
on	O
a	O
head-per-track	O
magnetic	B-Device
disk	I-Device
called	O
a	O
RAD	O
(	O
Rapid	O
Access	O
Data	O
)	O
File	O
.	O
</s>
<s>
By	O
1969	O
an	O
ALGOL	B-Language
60	I-Language
compiler	O
was	O
available	O
.	O
</s>
