<s>
BogoMips	B-Application
(	O
from	O
"	O
bogus	O
"	O
and	O
MIPS	O
)	O
is	O
a	O
crude	O
measurement	O
of	O
CPU	B-General_Concept
speed	O
made	O
by	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
when	O
it	O
boots	O
to	O
calibrate	O
an	O
internal	O
busy-loop	B-Operating_System
.	O
</s>
<s>
BogoMips	B-Application
is	O
a	O
value	O
that	O
can	O
be	O
used	O
to	O
verify	O
whether	O
the	O
processor	O
in	O
question	O
is	O
in	O
the	O
proper	O
range	O
of	O
similar	O
processors	O
,	O
i.e.	O
</s>
<s>
BogoMips	B-Application
represents	O
a	O
processor	O
's	O
clock	O
frequency	O
as	O
well	O
as	O
the	O
potentially	O
present	O
CPU	B-General_Concept
cache	I-General_Concept
.	O
</s>
<s>
In	O
1993	O
,	O
Lars	O
Wirzenius	O
posted	O
a	O
Usenet	B-Application
message	O
explaining	O
the	O
reasons	O
for	O
its	O
introduction	O
in	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
on	O
comp.os.linux	O
:	O
</s>
<s>
BogoMips	B-Application
are	O
Linus	O
's	O
own	O
invention	O
.	O
</s>
<s>
The	O
linux	B-Operating_System
kernel	I-Operating_System
version	O
0.99.11	O
(	O
dated	O
11	O
July	O
1993	O
)	O
needed	O
a	O
timing	O
loop	O
(	O
the	O
time	O
is	O
too	O
short	O
and/or	O
needs	O
to	O
be	O
too	O
exact	O
for	O
a	O
non-busy-loop	O
method	O
of	O
waiting	O
)	O
,	O
which	O
must	O
be	O
calibrated	O
to	O
the	O
processor	O
speed	O
of	O
the	O
machine	O
.	O
</s>
<s>
Hence	O
,	O
the	O
kernel	B-Operating_System
measures	O
at	O
boot	O
time	O
how	O
fast	O
a	O
certain	O
kind	O
of	O
busy	B-Operating_System
loop	I-Operating_System
runs	O
on	O
a	O
computer	O
.	O
</s>
<s>
Hence	O
,	O
the	O
BogoMips	B-Application
value	O
gives	O
some	O
indication	O
of	O
the	O
processor	O
speed	O
,	O
but	O
it	O
is	O
way	O
too	O
unscientific	O
to	O
be	O
called	O
anything	O
but	O
BogoMips	B-Application
.	O
</s>
<s>
The	O
reasons	O
(	O
there	O
are	O
two	O
)	O
it	O
is	O
printed	O
during	O
boot-up	O
is	O
that	O
a	O
)	O
it	O
is	O
slightly	O
useful	O
for	O
debugging	O
and	O
for	O
checking	O
that	O
the	O
computer[’]s	O
caches	O
and	O
turbo	B-Device
button	I-Device
work	O
,	O
and	O
b	O
)	O
Linus	O
loves	O
to	O
chuckle	O
when	O
he	O
sees	O
confused	O
people	O
on	O
the	O
news	O
.	O
</s>
<s>
As	O
a	O
very	O
approximate	O
guide	O
,	O
the	O
BogoMips	B-Application
can	O
be	O
pre-calculated	O
by	O
the	O
following	O
table	O
.	O
</s>
<s>
The	O
given	O
rating	O
is	O
typical	O
for	O
that	O
CPU	B-General_Concept
with	O
the	O
then	O
current	O
and	O
applicable	O
Linux	B-Operating_System
version	O
.	O
</s>
<s>
The	O
index	O
is	O
the	O
ratio	O
of	O
"	O
BogoMips	B-Application
per	O
clock	O
speed	O
"	O
for	O
any	O
CPU	B-General_Concept
to	O
the	O
same	O
for	O
an	O
Intel	O
386DX	B-General_Concept
CPU	B-General_Concept
,	O
for	O
comparison	O
purposes	O
.	O
</s>
<s>
With	O
the	O
2.2.14	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
a	O
caching	B-General_Concept
setting	O
of	O
the	O
CPU	B-General_Concept
state	O
was	O
moved	O
from	O
behind	O
to	O
before	O
the	O
BogoMips	B-Application
calculation	O
.	O
</s>
<s>
Although	O
the	O
BogoMips	B-Application
algorithm	O
itself	O
was	O
n't	O
changed	O
,	O
from	O
that	O
kernel	B-Operating_System
onward	O
the	O
BogoMips	B-Application
rating	O
for	O
then	O
current	O
Pentium	B-General_Concept
CPUs	O
was	O
twice	O
that	O
of	O
the	O
rating	O
before	O
the	O
change	O
.	O
</s>
<s>
The	O
changed	O
BogoMips	B-Application
outcome	O
had	O
no	O
effect	O
on	O
real	O
processor	O
performance	O
.	O
</s>
<s>
In	O
Linux	B-Operating_System
,	O
BogoMips	B-Application
can	O
be	O
easily	O
obtained	O
by	O
searching	O
the	O
cpuinfo	O
file	O
:	O
</s>
<s>
With	O
kernel	B-Operating_System
2.6.x	O
,	O
BogoMIPS	B-Application
are	O
implemented	O
in	O
the	O
/usr/src/linux/init/calibrate.c	O
kernel	B-Operating_System
source	O
file	O
.	O
</s>
<s>
It	O
computes	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
timing	O
parameter	O
loops_per_jiffy	O
(	O
see	O
jiffy	B-Operating_System
)	O
value	O
.	O
</s>
<s>
Note	O
that	O
a	O
busy	B-Operating_System
waiting	I-Operating_System
technique	O
is	O
used	O
,	O
so	O
the	O
kernel	B-Operating_System
is	O
effectively	O
blocked	O
when	O
executing	O
ndelay/udelay	O
functions	O
.	O
</s>
<s>
For	O
i386	B-General_Concept
architecture	O
delay_loop	O
is	O
implemented	O
in	O
/usr/src/linux/arch/i386/lib/delay.c	O
as	O
:	O
</s>
<s>
Full	O
and	O
complete	O
information	O
and	O
details	O
about	O
BogoMips	B-Application
,	O
and	O
hundreds	O
of	O
reference	O
entries	O
can	O
be	O
found	O
in	O
the	O
(	O
outdated	O
)	O
BogoMips	B-Application
mini-Howto	O
.	O
</s>
<s>
In	O
2012	O
,	O
ARM	B-Architecture
contributed	O
a	O
new	O
udelay	O
implementation	O
allowing	O
the	O
system	O
timer	O
built	O
into	O
many	O
ARMv7	O
CPUs	O
to	O
be	O
used	O
instead	O
of	O
a	O
busy-wait	B-Operating_System
loop	I-Operating_System
.	O
</s>
<s>
This	O
implementation	O
was	O
released	O
in	O
Version	O
3.6	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
Timer-based	O
delays	O
are	O
more	O
robust	O
on	O
systems	O
that	O
use	O
frequency	B-General_Concept
scaling	I-General_Concept
to	O
dynamically	O
adjust	O
the	O
processor	O
's	O
speed	O
at	O
runtime	O
,	O
as	O
loops_per_jiffies	O
values	O
may	O
not	O
necessarily	O
scale	O
linearly	O
.	O
</s>
<s>
One	O
side	O
effect	O
of	O
this	O
change	O
is	O
that	O
the	O
BogoMIPS	B-Application
value	O
will	O
reflect	O
the	O
timer	O
frequency	O
,	O
not	O
the	O
CPU	B-General_Concept
's	O
core	O
frequency	O
.	O
</s>
<s>
Typically	O
the	O
timer	O
frequency	O
is	O
much	O
lower	O
than	O
the	O
processor	O
's	O
maximum	O
frequency	O
,	O
and	O
some	O
users	O
may	O
be	O
surprised	O
to	O
see	O
an	O
unusually	O
low	O
BogoMIPS	B-Application
value	O
when	O
comparing	O
against	O
systems	O
that	O
use	O
traditional	O
busy-wait	B-Operating_System
loops	I-Operating_System
.	O
</s>
