<s>
The	O
GE-600	B-Device
series	I-Device
was	O
a	O
family	O
of	O
36-bit	O
mainframe	B-Architecture
computers	I-Architecture
originating	O
in	O
the	O
1960s	O
,	O
built	O
by	O
General	O
Electric	O
(	O
GE	O
)	O
.	O
</s>
<s>
When	O
GE	O
left	O
the	O
mainframe	B-Architecture
business	O
the	O
line	O
was	O
sold	O
to	O
Honeywell	O
,	O
which	O
built	O
similar	O
systems	O
into	O
the	O
1990s	O
as	O
the	O
division	O
moved	O
to	O
Groupe	O
Bull	O
and	O
then	O
NEC	O
.	O
</s>
<s>
The	O
system	O
is	O
perhaps	O
best	O
known	O
as	O
the	O
hardware	O
used	O
by	O
the	O
Dartmouth	B-Operating_System
Time	I-Operating_System
Sharing	I-Operating_System
System	I-Operating_System
(	O
DTSS	O
)	O
and	O
the	O
Multics	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Multics	B-Application
was	O
supported	O
by	O
virtual	B-Architecture
memory	I-Architecture
additions	O
made	O
to	O
later	O
versions	O
of	O
the	O
series	O
.	O
</s>
<s>
They	O
had	O
two	O
36-bit	O
accumulators	B-General_Concept
,	O
eight	O
18-bit	O
index	B-General_Concept
registers	I-General_Concept
,	O
and	O
one	O
8-bit	O
exponent	O
register	O
.	O
</s>
<s>
It	O
supported	O
floating	B-Algorithm
point	I-Algorithm
in	O
both	O
36-bit	O
single-precision	O
and	O
2	O
x	O
36-bit	O
double	O
precision	O
,	O
the	O
exponent	O
being	O
stored	O
separately	O
,	O
allowing	O
up	O
to	O
71	O
bits	O
of	O
precision	O
and	O
one	O
bit	O
being	O
used	O
for	O
the	O
sign	O
.	O
</s>
<s>
It	O
had	O
an	O
elaborate	O
set	O
of	O
addressing	B-Language
modes	I-Language
,	O
many	O
of	O
which	O
used	O
indirect	B-Language
words	I-Language
,	O
some	O
of	O
which	O
were	O
auto-incrementing	O
or	O
auto-decrementing	O
.	O
</s>
<s>
It	O
supported	O
6-bit	O
and	O
9-bit	O
bytes	B-Application
through	O
addressing	B-Language
modes	I-Language
;	O
these	O
supported	O
extracting	O
specific	O
bytes	B-Application
,	O
and	O
incrementing	O
the	O
byte	B-Application
pointer	O
,	O
but	O
not	O
random	O
access	O
to	O
bytes	B-Application
.	O
</s>
<s>
It	O
also	O
included	O
a	O
number	O
of	O
channel	B-Device
controllers	I-Device
for	O
handling	O
I/O	B-General_Concept
.	O
</s>
<s>
The	O
CPU	B-General_Concept
could	O
hand	O
off	O
short	O
programs	O
written	O
in	O
the	O
channel	B-Device
controller	I-Device
's	O
own	O
machine	B-Language
language	I-Language
,	O
which	O
would	O
then	O
process	O
the	O
data	O
,	O
move	O
it	O
to	O
or	O
from	O
the	O
memory	O
,	O
and	O
raise	O
an	O
interrupt	B-Application
when	O
they	O
completed	O
.	O
</s>
<s>
This	O
allowed	O
the	O
main	O
CPU	B-General_Concept
to	O
move	O
on	O
to	O
other	O
tasks	O
while	O
waiting	O
for	O
the	O
slow	O
I/O	B-General_Concept
to	O
complete	O
,	O
a	O
primary	O
feature	O
of	O
time	B-General_Concept
sharing	I-General_Concept
systems	O
.	O
</s>
<s>
Originally	O
the	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
600-series	O
computers	O
was	O
GECOS	B-Application
,	O
developed	O
by	O
GE	O
beginning	O
in	O
1962	O
.	O
</s>
<s>
GECOS	B-Application
was	O
initially	O
a	O
batch	B-General_Concept
processing	I-General_Concept
system	O
,	O
but	O
later	O
added	O
many	O
features	O
seen	O
on	O
more	O
modern	O
systems	O
,	O
including	O
multitasking	B-Operating_System
and	O
multi-user	O
support	O
.	O
</s>
<s>
Between	O
1963	O
and	O
1964	O
,	O
GE	O
worked	O
with	O
Dartmouth	O
College	O
on	O
their	O
Dartmouth	B-Language
BASIC	I-Language
project	O
,	O
which	O
also	O
led	O
to	O
the	O
development	O
of	O
a	O
new	O
timesharing	B-General_Concept
system	O
to	O
support	O
it	O
on	O
the	O
GE-235	O
.	O
</s>
<s>
"	O
Phase	O
II	O
"	O
at	O
Dartmouth	O
was	O
released	O
as	O
the	O
Dartmouth	B-Operating_System
Time	I-Operating_System
Sharing	I-Operating_System
System	I-Operating_System
(	O
DTSS	O
)	O
,	O
while	O
GE	O
further	O
developed	O
Mark	O
II	O
into	O
the	O
improved	O
Mark	O
III	O
.	O
</s>
<s>
In	O
1965	O
,	O
Warner	O
Sinback	O
recommended	O
that	O
they	O
begin	O
to	O
sell	O
time-sharing	B-General_Concept
services	O
using	O
the	O
time-sharing	B-General_Concept
system	I-General_Concept
(	O
Mark	O
1	O
)	O
developed	O
at	O
Dartmouth	O
on	O
a	O
General	O
Electric	O
265	O
computer	O
.	O
</s>
<s>
The	O
service	O
was	O
an	O
instant	O
success	O
and	O
by	O
1968	O
,	O
GEIS	O
had	O
40%	O
of	O
the	O
$	O
70	O
million	O
time-sharing	B-General_Concept
market	O
.	O
</s>
<s>
The	O
service	O
continued	O
to	O
grow	O
,	O
and	O
over	O
time	O
migrated	O
to	O
the	O
GE	O
developed	O
Mark	O
II	O
and	O
Mark	O
III	O
operating	B-General_Concept
systems	I-General_Concept
running	O
on	O
large	O
mainframe	B-Architecture
computers	I-Architecture
.	O
</s>
<s>
The	O
GE	O
Mark	O
II	O
operating	B-General_Concept
system	I-General_Concept
(	O
later	O
Mark	O
III	O
)	O
was	O
used	O
by	O
GE	O
Information	O
Services	O
as	O
the	O
basis	O
for	O
its	O
timesharing	B-General_Concept
and	O
networked	O
computing	O
business	O
.	O
</s>
<s>
Mark	O
II/III	O
incorporated	O
many	O
features	O
normally	O
associated	O
with	O
on-line	O
transaction-processing	O
systems	O
,	O
such	O
as	O
journalization	O
and	O
granular	O
file	B-Application
locking	I-Application
.	O
</s>
<s>
In	O
the	O
early-to-mid-1970s	O
,	O
Mark	O
III	O
adopted	O
a	O
high-reliability	O
cluster	O
technology	O
,	O
in	O
which	O
up	O
to	O
eight	O
processing	O
systems	O
(	O
each	O
with	O
its	O
own	O
copy	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
)	O
had	O
access	O
to	O
multiple	O
file	O
systems	O
.	O
</s>
<s>
The	O
Multics	B-Application
operating	I-Application
system	I-Application
was	O
begun	O
in	O
1964	O
as	O
an	O
advanced	O
new	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
600	O
series	O
,	O
though	O
it	O
was	O
not	O
production-ready	O
until	O
1969	O
.	O
</s>
<s>
Multics	B-Application
required	O
a	O
number	O
of	O
additional	O
features	O
in	O
the	O
CPU	B-General_Concept
to	O
be	O
truly	O
effective	O
,	O
and	O
John	O
Couleur	O
was	O
joined	O
by	O
Edward	O
Glaser	O
at	O
MIT	O
to	O
make	O
the	O
required	O
modifications	O
.	O
</s>
<s>
The	O
result	O
was	O
the	O
GE	B-Device
645	I-Device
,	O
which	O
included	O
support	O
for	O
virtual	B-Architecture
memory	I-Architecture
.	O
</s>
<s>
Addressing	O
was	O
modified	O
to	O
use	O
an	O
18-bit	O
segment	O
in	O
addition	O
to	O
the	O
18-bit	O
address	O
,	O
dramatically	O
increasing	O
the	O
theoretical	O
memory	O
size	O
and	O
making	O
virtual	B-Architecture
memory	I-Architecture
much	O
easier	O
to	O
support	O
.	O
</s>
<s>
MISTRAM	O
was	O
a	O
radar	B-Application
tracking	O
system	O
that	O
was	O
used	O
on	O
a	O
number	O
of	O
projects	O
,	O
including	O
Project	O
Apollo	O
.	O
</s>
<s>
The	O
data	O
would	O
eventually	O
be	O
shared	O
with	O
the	O
36-bit	O
IBM	B-Device
7094	I-Device
machine	O
at	O
the	O
Cape	O
,	O
so	O
the	O
computer	O
would	O
likely	O
have	O
to	O
be	O
36-bits	O
as	O
well	O
.	O
</s>
<s>
However	O
,	O
by	O
the	O
early	O
1960s	O
GE	O
was	O
the	O
largest	O
user	O
of	O
IBM	B-Device
mainframes	I-Device
,	O
and	O
producing	O
their	O
own	O
machines	O
seemed	O
like	O
an	O
excellent	O
way	O
to	O
lower	O
the	O
costs	O
of	O
their	O
computing	O
department	O
.	O
</s>
<s>
The	O
machine	O
was	O
originally	O
offered	O
as	O
the	O
main	O
GE-635	B-Device
,	O
and	O
the	O
slower	O
but	O
compatible	O
GE-625	B-Device
and	O
GE-615	B-Device
.	O
</s>
<s>
While	O
most	O
were	O
single-processor	O
systems	O
,	O
the	O
635	O
could	O
be	O
configured	O
with	O
four	O
CPUs	O
and	O
up	O
to	O
four	O
input/output	B-General_Concept
controllers	O
(	O
IOC	O
's	O
)	O
each	O
with	O
up	O
to	O
16	O
Common	O
Peripheral	O
Interface	O
Channels	O
.	O
</s>
<s>
The	O
635	O
was	O
likely	O
the	O
first	O
example	O
of	O
a	O
general	O
purpose	O
SMP	B-Operating_System
system	O
,	O
though	O
the	O
GECOS/GCOS	O
software	O
treated	O
the	O
processors	O
as	O
a	O
master	O
and	O
up	O
to	O
three	O
slaves	O
.	O
</s>
<s>
In	O
May	O
1965	O
the	O
first	O
GE-625	B-Device
computer	O
was	O
delivered	O
to	O
the	O
GE	O
Schenectady	O
plant	O
to	O
replace	O
five	O
other	O
computers	O
of	O
various	O
sizes	O
and	O
makes	O
.	O
</s>
<s>
A	O
number	O
of	O
GE	B-Device
635	I-Device
's	O
were	O
shipped	O
during	O
1965	O
including	O
two	O
to	O
Martin	O
Marietta	O
in	O
November	O
.	O
</s>
<s>
The	O
605	O
was	O
used	O
in	O
some	O
realtime/military	O
applications	O
and	O
was	O
essentially	O
a	O
615	O
without	O
the	O
floating	B-Algorithm
point	I-Algorithm
hardware	O
.	O
</s>
<s>
The	O
645	O
was	O
a	O
modified	O
635	O
processor	O
that	O
provided	O
hardware	O
support	O
for	O
the	O
Multics	B-Application
operating	I-Application
system	I-Application
developed	O
at	O
MIT	O
.	O
</s>
<s>
The	O
605/615/625/635	O
and	O
645	O
were	O
essentially	O
second	B-Device
generation	I-Device
computers	I-Device
with	O
discrete	O
transistor	B-Application
TTL	B-General_Concept
logic	I-General_Concept
and	O
a	O
handful	O
of	O
integrated	O
circuits	O
.	O
</s>
<s>
By	O
1967	O
these	O
problems	O
were	O
cleared	O
up	O
,	O
and	O
the	O
machines	O
were	O
re-launched	O
along	O
with	O
an	O
upgraded	O
version	O
of	O
the	O
GECOS	B-Application
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
new	O
GE-655	O
replaced	O
the	O
individual	O
transistors	B-Application
from	O
the	O
earlier	O
models	O
with	O
integrated	O
circuits	O
,	O
which	O
doubled	O
the	O
performance	O
of	O
the	O
machine	O
while	O
also	O
greatly	O
reducing	O
assembly	O
costs	O
.	O
</s>
<s>
By	O
that	O
time	O
the	O
Multics	B-Application
project	O
had	O
finally	O
produced	O
an	O
operating	B-General_Concept
system	I-General_Concept
usable	O
by	O
end-users	O
.	O
</s>
<s>
Besides	O
MIT	O
,	O
Bell	O
Labs	O
,	O
and	O
GE	O
,	O
GE-645	B-Device
systems	O
running	O
Multics	B-Application
were	O
installed	O
at	O
the	O
US	O
Air	O
Force	O
Rome	O
Development	O
Center	O
,	O
Honeywell	O
Billerica	O
,	O
and	O
Machines	O
Bull	O
in	O
Paris	O
.	O
</s>
<s>
GE	O
sold	O
its	O
computer	O
division	O
to	O
Honeywell	O
in	O
1970	O
,	O
who	O
renamed	O
the	O
GE-600	B-Device
series	I-Device
as	O
the	O
Honeywell	B-Device
6000	I-Device
series	I-Device
.	O
</s>
<s>
An	O
optional	O
Decimal/Business	O
instruction	O
set	O
was	O
added	O
to	O
improve	O
COBOL	B-Application
performance	O
.	O
</s>
<s>
A	O
version	O
of	O
the	O
6080	O
with	O
the	O
various	O
Multics-related	O
changes	O
similar	O
to	O
the	O
645	O
was	O
released	O
as	O
the	O
6180	O
.	O
</s>
