<s>
In	O
computing	O
,	O
legacy	B-Device
mode	I-Device
is	O
a	O
state	O
in	O
which	O
a	O
computer	O
system	O
,	O
component	O
,	O
or	O
software	O
application	O
behaves	O
in	O
a	O
way	O
that	O
is	O
different	O
from	O
its	O
standard	O
operation	O
in	O
order	O
to	O
support	O
older	O
software	O
,	O
data	O
,	O
or	O
expected	O
behavior	O
.	O
</s>
<s>
It	O
differs	O
from	O
backward	B-General_Concept
compatibility	I-General_Concept
in	O
that	O
an	O
item	O
in	O
legacy	B-Device
mode	I-Device
will	O
often	O
sacrifice	O
newer	O
features	O
or	O
performance	O
,	O
or	O
be	O
unable	O
to	O
access	O
data	O
or	O
run	O
programs	O
it	O
normally	O
could	O
,	O
in	O
order	O
to	O
provide	O
continued	O
access	O
to	O
older	O
data	O
or	O
functionality	O
.	O
</s>
<s>
Sometimes	O
it	O
can	O
allow	O
newer	O
technologies	O
that	O
replaced	O
the	O
old	O
to	O
emulate	O
them	O
when	O
running	O
older	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
x86-64	B-Device
processors	O
can	O
be	O
run	O
in	O
one	O
of	O
two	O
states	O
:	O
long	B-Application
mode	I-Application
provides	O
larger	O
physical	O
address	O
spaces	O
and	O
the	O
ability	O
to	O
run	O
64-bit	O
applications	O
which	O
can	O
use	O
larger	O
virtual	O
address	O
spaces	O
and	O
more	O
registers	O
,	O
and	O
legacy	B-Device
mode	I-Device
.	O
</s>
<s>
These	O
processors	O
 '	O
legacy	B-Device
mode	I-Device
allows	O
these	O
processors	O
to	O
act	O
as	O
if	O
they	O
were	O
16	O
-	O
or	O
32-bit	O
x86	B-Operating_System
processors	O
with	O
all	O
of	O
the	O
abilities	O
and	O
limitations	O
of	O
them	O
in	O
order	O
to	O
run	O
legacy	O
16-bit	O
and	O
32-bit	O
operating	B-General_Concept
systems	I-General_Concept
,	O
and	O
to	O
run	O
programs	O
requiring	O
virtual	B-Application
8086	I-Application
mode	I-Application
to	O
run	O
in	O
Windows	O
.	O
</s>
<s>
32-bit	O
x86	B-Operating_System
processors	O
themselves	O
have	O
two	O
legacy	B-Device
modes	I-Device
:	O
real	B-Application
mode	I-Application
and	O
virtual	B-Application
8086	I-Application
mode	I-Application
.	O
</s>
<s>
Real	B-Application
mode	I-Application
causes	O
the	O
processor	O
to	O
mostly	O
act	O
as	O
if	O
it	O
was	O
an	O
original	O
8086	O
,	O
while	O
virtual	B-Application
8086	I-Application
mode	I-Application
allows	O
the	O
creation	O
of	O
a	O
virtual	O
machine	O
to	O
allow	O
the	O
running	O
of	O
programs	O
that	O
require	O
real	B-Application
mode	I-Application
in	O
order	O
to	O
run	O
under	O
a	O
protected	B-Application
mode	I-Application
environment	O
.	O
</s>
<s>
Protected	B-Application
mode	I-Application
is	O
the	O
non-legacy	O
mode	O
of	O
32-bit	O
x86	B-Operating_System
processors	O
and	O
the	O
80286	O
.	O
</s>
<s>
Most	O
PC	B-Device
graphic	B-Device
cards	I-Device
have	O
a	O
VGA	B-Protocol
and	O
a	O
SVGA	O
mode	O
that	O
allows	O
them	O
to	O
be	O
used	O
on	O
systems	O
that	O
have	O
not	O
loaded	O
the	O
device	B-Application
driver	I-Application
necessary	O
to	O
take	O
advantage	O
of	O
their	O
more	O
advanced	O
features	O
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
often	O
have	O
a	O
special	O
mode	O
allowing	O
them	O
to	O
emulate	O
an	O
older	O
release	O
in	O
order	O
to	O
support	O
software	O
applications	O
dependent	O
on	O
the	O
specific	O
interfaces	O
and	O
behavior	O
of	O
that	O
release	O
.	O
</s>
<s>
Windows	B-Application
XP	I-Application
can	O
be	O
configured	O
to	O
emulate	O
Windows	B-Application
2000	I-Application
and	O
Windows	B-Device
98	I-Device
;	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
can	O
support	O
the	O
execution	O
of	O
Mac	B-Operating_System
OS	I-Operating_System
9	I-Operating_System
applications	O
on	O
PowerPC-based	O
Macintoshes	O
.	O
</s>
<s>
Computer	O
buses	O
emulated	O
through	O
legacy	B-Device
mode	I-Device
:	O
</s>
<s>
Many	O
SATA	O
disk	O
controllers	O
offer	O
a	O
legacy	B-Device
mode	I-Device
of	O
operation	O
for	O
compatibility	O
i.e.	O
</s>
<s>
Some	O
niche	O
markets	O
have	O
enabled	O
Compact	B-Device
Flash	I-Device
and	O
SD	B-Device
cards	I-Device
to	O
emulate	O
IDE	B-Protocol
hard	I-Protocol
drives	I-Protocol
for	O
old	O
DOS	B-Device
and	O
Windows	B-Application
95	I-Application
computers	O
.	O
</s>
<s>
The	B-Operating_System
Wii	I-Operating_System
U	O
can	O
be	O
run	O
in	O
a	O
special	O
"	O
Wii	B-Operating_System
Mode	O
"	O
that	O
activates	O
an	O
emulated	O
version	O
of	O
the	B-Operating_System
Wii	I-Operating_System
Menu	O
as	O
a	O
means	O
of	O
playing	O
games	O
made	O
for	O
the	O
latter	O
system	O
(	O
it	O
is	O
not	O
compatible	O
with	O
GameCube	B-Application
games	O
without	O
system	O
modification	O
,	O
however	O
)	O
.	O
</s>
