<s>
Open	B-Architecture
Firmware	I-Architecture
is	O
a	O
standard	O
defining	O
the	O
interfaces	O
of	O
a	O
computer	O
firmware	B-Application
system	O
,	O
formerly	O
endorsed	O
by	O
the	O
Institute	O
of	O
Electrical	O
and	O
Electronics	O
Engineers	O
(	O
IEEE	O
)	O
.	O
</s>
<s>
It	O
originated	O
at	O
Sun	O
Microsystems	O
,	O
where	O
it	O
was	O
known	O
as	O
OpenBoot	B-Architecture
,	O
and	O
has	O
been	O
used	O
by	O
vendors	O
including	O
Sun	O
,	O
Apple	O
,	O
IBM	O
and	O
ARM	O
.	O
</s>
<s>
Open	B-Architecture
Firmware	I-Architecture
allows	O
the	O
system	O
to	O
load	O
platform-independent	O
drivers	O
directly	O
from	O
a	O
PCI	B-Protocol
device	O
,	O
improving	O
compatibility	O
.	O
</s>
<s>
Open	B-Architecture
Firmware	I-Architecture
may	O
be	O
accessed	O
through	O
its	O
command	B-Application
line	I-Application
interface	I-Application
,	O
which	O
uses	O
the	O
Forth	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
Open	B-Architecture
Firmware	I-Architecture
is	O
described	O
by	O
IEEE	O
standard	O
IEEE	O
1275-1994	O
,	O
which	O
was	O
not	O
reaffirmed	O
by	O
the	O
Open	B-Architecture
Firmware	I-Architecture
Working	O
Group	O
(	O
OFWG	O
)	O
since	O
1998	O
and	O
has	O
therefore	O
been	O
officially	O
withdrawn	O
by	O
IEEE	O
.	O
</s>
<s>
Several	O
commercial	O
implementations	O
of	O
Open	B-Architecture
Firmware	I-Architecture
have	O
been	O
released	O
to	O
the	O
Open	O
Source	O
community	O
in	O
2006	O
,	O
including	O
Sun	O
OpenBoot	B-Architecture
,	O
Firmworks	O
OpenFirmware	B-Architecture
and	O
Codegen	O
SmartFirmware	O
.	O
</s>
<s>
The	O
source	O
code	O
is	O
available	O
from	O
the	O
OpenBIOS	B-Device
project	O
.	O
</s>
<s>
Sun	O
's	O
implementation	O
is	O
available	O
under	O
a	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Open	B-Architecture
Firmware	I-Architecture
defines	O
a	O
standard	O
way	O
to	O
describe	O
the	O
hardware	O
configuration	O
of	O
a	O
system	O
,	O
called	O
the	O
device	B-Operating_System
tree	I-Operating_System
.	O
</s>
<s>
For	O
example	O
,	O
Open	B-Architecture
Firmware	I-Architecture
is	O
essential	O
for	O
reliably	O
identifying	O
slave	O
I2C	O
devices	O
like	O
temperature	O
sensors	O
for	O
hardware	B-Application
monitoring	I-Application
,	O
whereas	O
the	O
alternative	O
solution	O
of	O
performing	O
a	O
blind	O
probe	O
of	O
the	O
I2C	O
bus	O
,	O
as	O
has	O
to	O
be	O
done	O
by	O
software	O
like	O
lm_sensors	O
on	O
generic	O
hardware	O
,	O
is	O
known	O
to	O
result	O
in	O
serious	O
hardware	O
issues	O
under	O
certain	O
circumstances	O
.	O
</s>
<s>
Open	B-Architecture
Firmware	I-Architecture
Forth	O
Code	O
may	O
be	O
compiled	O
into	O
FCode	B-Architecture
,	O
a	O
bytecode	O
which	O
is	O
independent	O
of	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
.	O
</s>
<s>
A	O
PCI	B-Protocol
card	I-Protocol
may	O
include	O
a	O
program	O
,	O
compiled	O
to	O
FCode	B-Architecture
,	O
which	O
runs	O
on	O
any	O
Open	B-Architecture
Firmware	I-Architecture
system	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
it	O
can	O
provide	O
boot-time	O
diagnostics	O
,	O
configuration	O
code	O
,	O
and	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
FCode	B-Architecture
is	O
also	O
very	O
compact	O
,	O
so	O
that	O
a	O
disk	O
driver	B-Application
may	O
require	O
only	O
one	O
or	O
two	O
kilobytes	O
.	O
</s>
<s>
Therefore	O
,	O
many	O
of	O
the	O
same	O
I/O	O
cards	O
can	O
be	O
used	O
on	O
Sun	O
systems	O
and	O
Macintoshes	O
that	O
used	O
Open	B-Architecture
Firmware	I-Architecture
.	O
</s>
<s>
FCode	B-Architecture
implements	O
ANS	B-Application
Forth	I-Application
and	O
a	O
subset	O
of	O
the	O
Open	B-Architecture
Firmware	I-Architecture
library	O
.	O
</s>
<s>
Being	O
based	O
upon	O
an	O
interactive	O
programming	O
language	O
,	O
Open	B-Architecture
Firmware	I-Architecture
can	O
be	O
used	O
to	O
efficiently	O
test	O
and	O
bring	O
up	O
new	O
hardware	O
.	O
</s>
<s>
Operational	O
video	O
and	O
mouse	O
drivers	O
are	O
the	O
only	O
prerequisite	O
for	O
a	O
graphical	B-Application
interface	I-Application
suitable	O
for	O
end-user	O
diagnostics	O
.	O
</s>
<s>
On	O
Sun	B-Architecture
SPARC	I-Architecture
systems	O
,	O
the	O
Open	B-Architecture
Firmware	I-Architecture
interface	O
is	O
displayed	O
on	O
the	O
console	O
terminal	O
before	O
the	O
bootstrapping	O
of	O
the	O
system	O
software	O
.	O
</s>
<s>
If	O
a	O
keyboard	O
is	O
connected	O
,	O
the	O
main	O
video	O
display	O
will	O
be	O
used	O
as	O
the	O
console	O
terminal	O
and	O
Open	B-Architecture
Firmware	I-Architecture
can	O
be	O
re-entered	O
at	O
any	O
time	O
by	O
pressing	O
(	O
)	O
on	O
the	O
keyboard	O
.	O
</s>
<s>
If	O
no	O
keyboard	O
is	O
connected	O
,	O
then	O
the	O
first	O
serial	O
line	O
on	O
the	O
system	O
is	O
usually	O
used	O
as	O
the	O
console	O
and	O
Open	B-Architecture
Firmware	I-Architecture
is	O
re-entered	O
by	O
sending	O
a	O
"	O
Break	O
"	O
on	O
the	O
serial	O
line	O
.	O
</s>
<s>
While	O
the	O
system	O
software	O
is	O
running	O
,	O
various	O
Open	B-Architecture
Firmware	I-Architecture
settings	O
can	O
be	O
read	O
or	O
written	O
using	O
the	O
eeprom	O
command	O
.	O
</s>
<s>
On	O
a	O
PowerPC-based	O
Macintosh	O
,	O
the	O
Open	B-Architecture
Firmware	I-Architecture
interface	O
can	O
be	O
accessed	O
by	O
pressing	O
the	O
keys	O
at	O
startup	O
(	O
if	O
using	O
standard	O
PC	O
USB	O
keyboard	O
)	O
.	O
</s>
<s>
Intel-based	B-Device
Macintoshes	I-Device
do	O
not	O
use	O
Open	B-Architecture
Firmware	I-Architecture
;	O
they	O
use	O
Extensible	B-Architecture
Firmware	I-Architecture
Interface	I-Architecture
.	O
</s>
<s>
Also	O
,	O
early	O
versions	O
(	O
before	O
the	O
PowerBook	B-Device
3400	I-Device
)	O
connect	O
Open	B-Architecture
Firmware	I-Architecture
's	O
input	O
and	O
output	O
to	O
the	O
Modem	O
port	O
by	O
default	O
.	O
</s>
<s>
personnel	O
;	O
for	O
common	O
users	O
,	O
the	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
operating	O
system	O
provides	O
a	O
high	O
level	O
graphical	B-Application
user	I-Application
interface	I-Application
to	O
change	O
commonly	O
used	O
Open	B-Architecture
Firmware	I-Architecture
settings	O
.	O
</s>
<s>
For	O
instance	O
,	O
it	O
is	O
possible	O
to	O
specify	O
the	O
boot	B-Operating_System
disk	I-Operating_System
or	O
partition	B-Application
without	O
directly	O
using	O
the	O
Open	B-Architecture
Firmware	I-Architecture
interface	O
,	O
but	O
with	O
some	O
limitations	O
(	O
e.g.	O
</s>
<s>
it	O
is	O
not	O
possible	O
to	O
select	O
boot	O
from	O
USB	O
mass-storage	O
devices	O
,	O
but	O
Open	B-Architecture
Firmware	I-Architecture
allows	O
iMac	O
to	O
boot	O
using	O
boot	O
ud	O
:	O
,	O
\\:tbxi	O
command	O
)	O
.	O
</s>
<s>
Other	O
Open	B-Architecture
Firmware	I-Architecture
settings	O
can	O
be	O
changed	O
using	O
the	O
nvram	B-General_Concept
command	O
while	O
the	O
system	O
software	O
is	O
running	O
.	O
</s>
<s>
On	O
Pegasos	B-Device
,	O
the	O
interface	O
is	O
accessed	O
by	O
pressing	O
at	O
startup	O
.	O
</s>
<s>
On	O
IBM	B-Device
Power	I-Device
Systems	I-Device
,	O
Open	B-Architecture
Firmware	I-Architecture
(	O
"	O
ok	O
"	O
prompt	O
)	O
can	O
be	O
accessed	O
through	O
the	O
SMS	O
Boot	O
Menu	O
.	O
</s>
<s>
On	O
the	O
OLPC	B-Application
XO-1	I-Application
laptop	O
,	O
Open	B-Architecture
Firmware	I-Architecture
access	O
requires	O
a	O
developer	O
key	O
,	O
that	O
can	O
be	O
obtained	O
after	O
registration	O
with	O
OLPC	O
.	O
</s>
