<s>
Cache	B-Operating_System
only	I-Operating_System
memory	I-Operating_System
architecture	I-Operating_System
(	O
COMA	O
)	O
is	O
a	O
computer	B-General_Concept
memory	I-General_Concept
organization	O
for	O
use	O
in	O
multiprocessors	B-Operating_System
in	O
which	O
the	O
local	O
memories	O
(	O
typically	O
DRAM	O
)	O
at	O
each	O
node	O
are	O
used	O
as	O
cache	O
.	O
</s>
<s>
This	O
is	O
in	O
contrast	O
to	O
using	O
the	O
local	O
memories	O
as	O
actual	O
main	O
memory	O
,	O
as	O
in	O
NUMA	B-Operating_System
organizations	O
.	O
</s>
<s>
In	O
NUMA	B-Operating_System
,	O
each	O
address	O
in	O
the	O
global	O
address	O
space	O
is	O
typically	O
assigned	O
a	O
fixed	O
home	O
node	O
.	O
</s>
<s>
Compared	O
to	O
NUMA	B-Operating_System
,	O
this	O
reduces	O
the	O
number	O
of	O
redundant	O
copies	O
and	O
may	O
allow	O
more	O
efficient	O
use	O
of	O
the	O
memory	O
resources	O
.	O
</s>
<s>
Hardware	O
memory	B-Operating_System
coherence	I-Operating_System
mechanisms	O
are	O
typically	O
used	O
to	O
implement	O
the	O
migration	O
.	O
</s>
<s>
Hybrid	O
NUMA-COMA	O
organizations	O
have	O
also	O
been	O
proposed	O
,	O
such	O
as	O
Reactive	O
NUMA	B-Operating_System
,	O
which	O
allows	O
pages	O
to	O
start	O
in	O
NUMA	B-Operating_System
mode	O
and	O
switch	O
to	O
COMA	O
mode	O
if	O
appropriate	O
and	O
is	O
implemented	O
in	O
the	O
Sun	O
Microsystems	O
's	O
WildFire	O
.	O
</s>
<s>
A	O
software-based	O
Hybrid	O
NUMA-COMA	O
implementation	O
was	O
proposed	O
and	O
implemented	O
by	O
ScaleMP	O
,	O
allowing	O
for	O
the	O
creation	O
of	O
a	O
shared-memory	O
multiprocessor	B-Operating_System
system	O
out	O
of	O
a	O
cluster	O
of	O
commodity	O
nodes	O
.	O
</s>
