<s>
The	O
MESIF	B-General_Concept
protocol	I-General_Concept
is	O
a	O
cache	B-General_Concept
coherency	I-General_Concept
and	O
memory	B-Operating_System
coherence	I-Operating_System
protocol	I-Operating_System
developed	O
by	O
Intel	O
for	O
cache	O
coherent	O
non-uniform	O
memory	O
architectures	O
.	O
</s>
<s>
The	O
M	O
,	O
E	O
,	O
S	O
and	O
I	O
states	O
are	O
the	O
same	O
as	O
in	O
the	O
MESI	B-General_Concept
protocol	I-General_Concept
.	O
</s>
<s>
In	O
a	O
system	O
of	O
caches	O
employing	O
the	O
MESI	B-General_Concept
protocol	I-General_Concept
,	O
a	O
cache	O
line	O
request	O
that	O
is	O
received	O
by	O
multiple	O
caches	O
holding	O
a	O
line	O
in	O
the	O
S	O
state	O
will	O
be	O
serviced	O
inefficiently	O
.	O
</s>
<s>
In	O
a	O
system	O
of	O
caches	O
employing	O
the	O
MESIF	B-General_Concept
protocol	I-General_Concept
,	O
a	O
cache	O
line	O
request	O
will	O
be	O
responded	O
to	O
only	O
by	O
the	O
cache	O
holding	O
the	O
line	O
in	O
the	O
F	O
state	O
.	O
</s>
<s>
Thus	O
,	O
the	O
main	O
difference	O
from	O
the	O
MESI	B-General_Concept
protocol	I-General_Concept
is	O
that	O
a	O
request	O
for	O
a	O
copy	O
of	O
the	O
cache	O
line	O
for	O
read	O
always	O
enters	O
the	O
cache	O
in	O
the	O
F	O
state	O
.	O
</s>
<s>
The	O
F	O
state	O
in	O
this	O
protocol	O
should	O
not	O
be	O
confused	O
with	O
the	O
"	O
Owner	O
"	O
O	O
state	O
in	O
the	O
MOESI	B-General_Concept
protocol	I-General_Concept
.	O
</s>
<s>
The	O
F	O
state	O
in	O
the	O
MESIF	B-General_Concept
protocol	I-General_Concept
is	O
simply	O
a	O
way	O
to	O
choose	O
one	O
of	O
the	O
sharers	O
of	O
a	O
clean	O
cache	O
line	O
to	O
respond	O
to	O
a	O
read	O
request	O
for	O
data	O
using	O
a	O
direct	O
cache-to-cache	O
transfer	O
instead	O
of	O
waiting	O
for	O
the	O
data	O
to	O
come	O
from	O
the	O
main	O
memory	O
.	O
</s>
<s>
A	O
key	O
point	O
to	O
be	O
noted	O
here	O
is	O
that	O
,	O
similar	O
to	O
the	O
MESI	B-General_Concept
protocol	I-General_Concept
,	O
when	O
data	O
is	O
in	O
the	O
shared	O
state	O
(	O
with	O
one	O
of	O
the	O
caches	O
in	O
the	O
F	O
state	O
)	O
the	O
data	O
is	O
clean	O
.	O
</s>
<s>
The	O
O	O
state	O
in	O
the	O
MOESI	B-General_Concept
protocol	I-General_Concept
is	O
an	O
optimization	O
to	O
the	O
MESI	B-General_Concept
protocol	I-General_Concept
where	O
the	O
requirement	O
of	O
the	O
shared	O
data	O
to	O
be	O
clean	O
is	O
relaxed	O
.	O
</s>
<s>
The	O
key	O
difference	O
in	O
the	O
MOESI	B-General_Concept
protocol	I-General_Concept
is	O
that	O
,	O
unlike	O
the	O
MESIF	B-General_Concept
protocol	I-General_Concept
,	O
the	O
Owned	O
state	O
is	O
not	O
clean	O
.	O
</s>
