<s>
Catamount	B-Operating_System
is	O
an	O
operating	B-General_Concept
system	I-General_Concept
for	O
supercomputers	B-Architecture
.	O
</s>
<s>
Catamount	B-Operating_System
is	O
a	O
lightweight	B-Device
kernel	I-Device
that	O
provides	O
basic	O
functionality	O
and	O
aims	O
for	O
efficiency	O
.	O
</s>
<s>
The	O
roots	O
of	O
Catamount	B-Operating_System
go	O
back	O
to	O
1991	O
when	O
SUNMOS	O
was	O
developed	O
by	O
Sandia	O
National	O
Laboratories	O
and	O
the	O
University	O
of	O
New	O
Mexico	O
as	O
a	O
lightweight	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
Cray	B-Device
XT3	I-Device
uses	O
Catamount	B-Operating_System
on	O
compute	O
nodes	O
and	O
Linux	B-Application
on	O
server	O
nodes	O
.	O
</s>
<s>
A	O
case	O
study	O
by	O
the	O
IEEE	O
assessed	O
the	O
performance	O
of	O
a	O
particle	O
transport	O
code	O
on	O
AWE	O
's	O
Cray	B-Device
XT3	I-Device
8,000	O
-core	O
supercomputer	B-Architecture
while	O
running	O
images	O
of	O
the	O
Catamount	B-Operating_System
and	O
the	O
Cray	O
Linux	B-Application
Environment	O
(	O
CLE	O
)	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
This	O
work	O
demonstrated	O
that	O
by	O
running	O
a	O
number	O
of	O
small	O
benchmarks	O
on	O
a	O
test	O
machine	O
it	O
is	O
possible	O
to	O
speculate	O
as	O
to	O
the	O
performance	O
impact	O
of	O
upgrading	B-General_Concept
from	O
one	O
operating	B-General_Concept
system	I-General_Concept
to	O
another	O
on	O
the	O
system	O
as	O
a	O
whole	O
.	O
</s>
<s>
The	O
study	O
's	O
findings	O
allows	O
researchers	O
to	O
minimise	O
system	O
downtime	O
while	O
exploring	O
software-system	O
upgrades	B-General_Concept
.	O
</s>
<s>
The	O
results	O
show	O
that	O
benchmark	O
tests	O
run	O
on	O
less	O
than	O
256	O
cores	O
would	O
suggest	O
that	O
the	O
impact	O
of	O
upgrading	B-General_Concept
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
CLE	O
was	O
less	O
than	O
10%	O
.	O
</s>
