<s>
The	O
Edinburgh	O
Multi-Access	O
System	O
(	O
EMAS	O
)	O
was	O
a	O
mainframe	B-Architecture
computer	I-Architecture
operating	B-General_Concept
system	I-General_Concept
at	O
the	O
University	O
of	O
Edinburgh	O
.	O
</s>
<s>
EMAS	O
was	O
a	O
powerful	O
and	O
efficient	O
general	O
purpose	O
multi-user	B-Operating_System
system	I-Operating_System
which	O
coped	O
with	O
many	O
of	O
the	O
computing	O
needs	O
of	O
the	O
University	O
of	O
Edinburgh	O
and	O
the	O
University	O
of	O
Kent	O
(	O
the	O
only	O
other	O
site	O
outside	O
Edinburgh	O
to	O
adopt	O
the	O
operating	B-General_Concept
system	I-General_Concept
)	O
.	O
</s>
<s>
Originally	O
running	O
on	O
the	O
ICL	B-Device
System	I-Device
4/75	I-Device
mainframe	B-Architecture
(	O
based	O
on	O
the	O
design	O
of	O
the	O
IBM	B-Application
360	I-Application
)	O
it	O
was	O
later	O
reimplemented	O
on	O
the	O
ICL	B-Device
2900	I-Device
series	I-Device
of	I-Device
mainframes	I-Device
(	O
as	O
EMAS	O
2900	O
or	O
EMAS-2	O
)	O
where	O
it	O
ran	O
in	O
service	O
until	O
the	O
mid-1980s	O
.	O
</s>
<s>
Near	O
the	O
end	O
of	O
its	O
life	O
,	O
the	O
refactored	O
version	O
was	O
back-ported	O
(	O
as	O
EMAS-3	O
)	O
to	O
the	O
Amdahl	O
470	O
mainframe	B-Architecture
clone	O
,	O
and	O
thence	O
to	O
the	O
IBM	B-Device
System/370	I-Device
-XA	I-Device
architecture	O
(	O
the	O
latter	O
with	O
help	O
from	O
the	O
University	O
of	O
Kent	O
,	O
although	O
they	O
never	O
actually	O
ran	O
EMAS-3	O
)	O
.	O
</s>
<s>
The	O
National	O
Advanced	O
System	O
(	O
NAS	O
)	O
VL80	O
IBM	O
mainframe	B-Architecture
clone	O
followed	O
later	O
.	O
</s>
<s>
The	O
University	O
of	O
Kent	O
system	O
went	O
live	O
in	O
December	O
1979	O
,	O
and	O
ran	O
on	O
the	O
least	O
powerful	O
machine	O
in	O
the	O
ICL	B-Device
2900	I-Device
range	O
-	O
an	O
ICL	B-Device
2960	I-Device
,	O
with	O
2	O
MB	O
of	O
memory	O
,	O
executing	O
about	O
290k	O
instructions	O
per	O
second	O
.	O
</s>
<s>
This	O
number	O
increased	O
in	O
1983	O
with	O
the	O
addition	O
of	O
an	O
additional	O
2	O
MB	O
of	O
memory	O
and	O
a	O
second	O
Order	O
Code	O
Processor	O
(	O
OCP	O
)	O
(	O
what	O
is	O
normally	O
known	O
as	O
a	O
CPU	O
)	O
running	O
with	O
symmetric	B-Operating_System
multiprocessing	I-Operating_System
.	O
</s>
<s>
It	O
had	O
several	O
features	O
that	O
were	O
advanced	O
for	O
the	O
time	O
,	O
including	O
dynamic	B-Application
linking	I-Application
,	O
multi-level	O
storage	O
,	O
an	O
efficient	O
scheduler	O
,	O
a	O
separate	O
user-space	O
kernel	B-Operating_System
( 	O
 '	O
director	O
 '	O
)	O
,	O
a	O
user-level	O
shell	B-Operating_System
( 	O
 '	O
basic	O
command	O
interpreter	O
 '	O
)	O
,	O
a	O
comprehensive	O
archiving	O
system	O
and	O
a	O
memory-mapped	B-General_Concept
file	I-General_Concept
architecture	O
.	O
</s>
<s>
Such	O
features	O
led	O
EMAS	O
supporters	O
to	O
claim	O
that	O
their	O
system	O
was	O
superior	O
to	O
Unix	B-Application
for	O
the	O
first	O
20	O
years	O
of	O
the	O
latter	O
's	O
existence	O
.	O
</s>
