<s>
A	O
model-specific	B-General_Concept
register	I-General_Concept
(	O
MSR	O
)	O
is	O
any	O
of	O
various	O
control	B-Operating_System
registers	I-Operating_System
in	O
the	O
x86	B-Operating_System
instruction	B-General_Concept
set	I-General_Concept
used	O
for	O
debugging	O
,	O
program	O
execution	O
tracing	O
,	O
computer	O
performance	O
monitoring	O
,	O
and	O
toggling	O
certain	O
CPU	B-Device
features	O
.	O
</s>
<s>
The	O
first	O
of	O
these	O
were	O
two	O
"	O
test	O
registers	O
"	O
(	O
TR6	O
and	O
TR7	O
)	O
that	O
enabled	O
testing	O
of	O
the	O
processor	O
's	O
translation	B-Architecture
lookaside	I-Architecture
buffer	I-Architecture
(	O
TLB	O
)	O
;	O
a	O
special	O
variant	O
of	O
the	O
instruction	O
allowed	O
moving	O
to	O
and	O
from	O
the	O
test	O
registers	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
the	O
Pentium	O
processor	O
,	O
Intel	O
provided	O
a	O
pair	O
of	O
instructions	O
(	O
and	O
)	O
to	O
access	O
current	O
and	O
future	O
"	O
model-specific	B-General_Concept
registers	I-General_Concept
"	O
,	O
as	O
well	O
as	O
the	O
instruction	O
to	O
determine	O
which	O
features	O
are	O
present	O
on	O
a	O
particular	O
model	O
.	O
</s>
<s>
Intel	O
has	O
classified	O
these	O
as	O
architectural	O
model-specific	B-General_Concept
registers	I-General_Concept
and	O
has	O
committed	O
to	O
their	O
inclusion	O
in	O
future	O
product	O
lines	O
.	O
</s>
<s>
Reading	O
and	O
writing	O
to	O
these	O
registers	O
is	O
handled	O
by	O
the	O
rdmsr	B-General_Concept
and	O
wrmsr	B-General_Concept
instructions	O
,	O
respectively	O
.	O
</s>
<s>
Use	O
of	O
the	O
Linux	O
msr	O
kernel	O
module	O
creates	O
a	O
pseudo	O
file	O
"	O
/dev/cpu/x/msr	O
"	O
(	O
with	O
a	O
unique	O
x	O
for	O
each	O
processor	O
or	O
processor	O
core	O
)	O
.	O
</s>
<s>
Documentation	O
regarding	O
which	O
MSRs	O
a	O
certain	O
processor	O
implementation	O
supports	O
is	O
usually	O
found	O
in	O
the	O
processor	O
documentation	O
of	O
the	O
CPU	B-Device
vendor	O
.	O
</s>
<s>
Examples	O
for	O
rather	O
well-known	O
MSRs	O
are	O
the	O
memory	B-General_Concept
type	I-General_Concept
range	I-General_Concept
registers	I-General_Concept
(	O
MTRRs	O
)	O
and	O
the	O
address-range	B-General_Concept
registers	I-General_Concept
(	O
ARRs	O
)	O
.	O
</s>
