<s>
On	O
the	O
x86	B-Operating_System
computer	B-General_Concept
architecture	I-General_Concept
,	O
a	O
triple	B-Error_Name
fault	I-Error_Name
is	O
a	O
special	O
kind	O
of	O
exception	B-General_Concept
generated	O
by	O
the	O
CPU	B-General_Concept
when	O
an	O
exception	B-General_Concept
occurs	O
while	O
the	O
CPU	B-General_Concept
is	O
trying	O
to	O
invoke	O
the	O
double	B-General_Concept
fault	I-General_Concept
exception	B-General_Concept
handler	I-General_Concept
,	O
which	O
itself	O
handles	O
exceptions	O
occurring	O
while	O
trying	O
to	O
invoke	O
a	O
regular	O
exception	B-General_Concept
handler	I-General_Concept
.	O
</s>
<s>
x86	B-Operating_System
processors	O
beginning	O
with	O
the	O
80286	B-General_Concept
will	O
cause	O
a	O
shutdown	O
cycle	O
to	O
occur	O
when	O
a	O
triple	B-Error_Name
fault	I-Error_Name
is	O
encountered	O
.	O
</s>
<s>
This	O
typically	O
causes	O
the	O
motherboard	B-Device
hardware	O
to	O
initiate	O
a	O
CPU	B-General_Concept
reset	O
,	O
which	O
,	O
in	O
turn	O
,	O
causes	O
the	O
whole	O
computer	O
to	O
reboot	O
.	O
</s>
<s>
Triple	B-Error_Name
faults	I-Error_Name
indicate	O
a	O
problem	O
with	O
the	O
operating	B-Operating_System
system	I-Operating_System
kernel	I-Operating_System
or	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
In	O
modern	O
operating	B-General_Concept
systems	I-General_Concept
,	O
a	O
triple	B-Error_Name
fault	I-Error_Name
is	O
typically	O
caused	O
by	O
a	O
buffer	O
overflow	O
or	O
underflow	O
in	O
a	O
device	B-Application
driver	I-Application
which	O
writes	O
over	O
the	O
interrupt	B-General_Concept
descriptor	I-General_Concept
table	I-General_Concept
(	O
IDT	O
)	O
.	O
</s>
<s>
If	O
the	O
IDT	O
is	O
corrupted	O
,	O
when	O
the	O
next	O
interrupt	B-Application
happens	O
,	O
the	O
processor	O
will	O
be	O
unable	O
to	O
call	O
either	O
the	O
needed	O
interrupt	B-Application
handler	O
or	O
the	O
double	B-General_Concept
fault	I-General_Concept
handler	O
because	O
the	O
descriptors	O
in	O
the	O
IDT	O
are	O
corrupted	O
.	O
</s>
<s>
In	O
QEMU	B-Application
,	O
a	O
triple	B-Error_Name
fault	I-Error_Name
produces	O
a	O
dump	O
of	O
the	O
virtual	O
machine	O
in	O
the	O
console	O
,	O
with	O
the	O
instruction	O
pointer	O
set	O
to	O
the	O
instruction	O
that	O
triggered	O
the	O
first	O
exception	B-General_Concept
.	O
</s>
<s>
When	O
using	O
Intel	O
VT-x	O
,	O
a	O
triple	B-Error_Name
fault	I-Error_Name
causes	O
a	O
VM	O
exit	O
,	O
with	O
exit	O
reason	O
2	O
.	O
</s>
<s>
The	O
Intel	B-General_Concept
80286	I-General_Concept
processor	O
was	O
the	O
first	O
x86	B-Operating_System
processor	O
to	O
introduce	O
the	O
now-ubiquitous	O
protected	B-Application
mode	I-Application
.	O
</s>
<s>
However	O
,	O
the	O
286	B-General_Concept
could	O
not	O
revert	O
to	O
the	O
basic	O
8086-compatible	O
"	O
real	B-Application
mode	I-Application
"	O
without	O
resetting	O
the	O
processor	O
,	O
which	O
can	O
only	O
be	O
done	O
using	O
hardware	O
external	O
to	O
the	O
CPU	B-General_Concept
.	O
</s>
<s>
On	O
the	O
IBM	B-Operating_System
AT	I-Operating_System
and	O
compatibles	O
,	O
the	O
documented	O
method	O
of	O
doing	O
this	O
was	O
to	O
use	O
a	O
special	O
function	O
on	O
the	O
Intel	B-Device
8042	I-Device
keyboard	O
controller	O
,	O
which	O
would	O
assert	O
the	O
RESET	O
pin	O
of	O
the	O
processor	O
.	O
</s>
<s>
However	O
,	O
intentionally	O
triple-faulting	O
the	O
CPU	B-General_Concept
was	O
found	O
to	O
cause	O
the	O
transition	O
to	O
occur	O
much	O
faster	O
and	O
more	O
cleanly	O
,	O
permitting	O
multitasking	O
operating	B-General_Concept
systems	I-General_Concept
to	O
switch	O
back	O
and	O
forth	O
at	O
high	O
speed	O
.	O
</s>
<s>
Some	O
operating	B-Operating_System
system	I-Operating_System
kernels	I-Operating_System
,	O
such	O
as	O
Linux	B-Operating_System
,	O
still	O
use	O
triple	B-Error_Name
faults	I-Error_Name
as	O
a	O
last	O
effort	O
in	O
their	O
rebooting	O
process	O
if	O
an	O
ACPI	B-Device
reboot	O
fails	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
setting	O
the	O
IDT	O
register	O
to	O
0	O
and	O
then	O
issuing	O
an	O
interrupt	B-Application
.	O
</s>
<s>
Since	O
the	O
table	O
now	O
has	O
length	O
0	O
,	O
all	O
attempts	O
to	O
access	O
it	O
fail	O
and	O
the	O
processor	O
generates	O
a	O
triple	B-Error_Name
fault	I-Error_Name
.	O
</s>
