<s>
Enforce	B-Device
In-order	I-Device
Execution	I-Device
of	I-Device
I/O	I-Device
(	O
EIEIO	O
)	O
is	O
an	O
assembly	B-Language
language	I-Language
instruction	O
used	O
on	O
the	O
PowerPC	B-Architecture
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
which	O
prevents	O
one	O
memory	O
or	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
operation	O
from	O
starting	O
until	O
the	O
previous	O
memory	O
or	O
I/O	B-General_Concept
operation	I-General_Concept
completed	O
.	O
</s>
<s>
This	O
instruction	O
is	O
needed	O
as	O
I/O	B-General_Concept
controllers	O
on	O
the	O
system	B-Architecture
bus	I-Architecture
require	O
that	O
accesses	O
follow	O
a	O
particular	O
order	O
,	O
while	O
the	O
CPU	O
reorders	O
accesses	O
to	O
optimize	O
memory	B-General_Concept
bandwidth	I-General_Concept
usage	O
.	O
</s>
