<s>
The	O
IBM	B-Device
AS/400	I-Device
(	O
Application	B-Device
System/400	I-Device
)	O
is	O
a	O
family	O
of	O
midrange	B-Device
computers	I-Device
from	O
IBM	O
announced	O
in	O
June	O
1988	O
and	O
released	O
in	O
August	O
1988	O
.	O
</s>
<s>
It	O
was	O
the	O
successor	O
to	O
the	O
System/36	B-Device
and	O
System/38	B-Device
platforms	O
,	O
and	O
ran	O
the	O
OS/400	B-Application
operating	O
system	O
.	O
</s>
<s>
Lower-cost	O
but	O
more	O
powerful	O
than	O
its	O
predecessors	O
,	O
the	O
AS/400	B-Device
was	O
extremely	O
successful	O
at	O
launch	O
,	O
with	O
an	O
estimated	O
111,000	O
installed	O
by	O
the	O
end	O
of	O
1990	O
and	O
annual	O
revenue	O
reaching	O
$14	O
billion	O
that	O
year	O
,	O
increasing	O
to	O
250,000	O
systems	O
by	O
1994	O
,	O
and	O
about	O
500,000	O
shipped	O
by	O
1997	O
.	O
</s>
<s>
A	O
key	O
concept	O
in	O
the	O
AS/400	B-Device
platform	O
is	O
Technology	O
Independent	O
Machine	O
Interface	O
(	O
TIMI	O
)	O
,	O
a	O
platform-independent	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
that	O
is	O
compiled	O
along	O
with	O
the	O
native	O
machine	B-Language
language	I-Language
instructions	O
.	O
</s>
<s>
Early	O
systems	O
were	O
based	O
on	O
a	O
48-bit	O
CISC	B-Architecture
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
known	O
as	O
the	O
Internal	O
Microprogrammed	O
Interface	O
(	O
IMPI	O
)	O
,	O
originally	O
developed	O
for	O
the	O
System/38	B-Device
.	O
</s>
<s>
In	O
1991	O
,	O
the	O
company	O
introduced	O
a	O
new	O
version	O
of	O
the	O
system	O
running	O
on	O
a	O
64-bit	B-Device
PowerPC-derived	O
CPU	O
,	O
the	O
IBM	B-Device
RS64	I-Device
.	O
</s>
<s>
Due	O
to	O
the	O
use	O
of	O
TIMI	O
,	O
applications	O
for	O
the	O
original	O
CISC-based	O
programs	O
continued	O
to	O
run	O
on	O
the	O
new	O
systems	O
without	O
modification	O
.	O
</s>
<s>
The	O
RS64	B-Device
was	O
replaced	O
with	O
POWER4	B-Device
processors	O
in	O
2001	O
,	O
which	O
was	O
followed	O
by	O
POWER5	B-Device
and	O
POWER6	B-Device
in	O
later	O
upgrades	O
.	O
</s>
<s>
The	O
AS/400	B-Device
went	O
through	O
multiple	O
re-branding	O
exercises	O
,	O
finally	O
becoming	O
the	O
System	O
i	O
in	O
2006	O
.	O
</s>
<s>
In	O
2008	O
,	O
IBM	O
consolidated	O
the	O
separate	O
System	O
i	O
and	O
System	B-Device
p	I-Device
product	O
lines	O
(	O
which	O
had	O
mostly	O
identical	O
hardware	O
by	O
that	O
point	O
)	O
into	O
a	O
single	O
product	O
line	O
named	O
IBM	B-Device
Power	I-Device
Systems	I-Device
.	O
</s>
<s>
The	O
name	O
"	O
AS/400	B-Device
"	O
is	O
sometimes	O
used	O
informally	O
to	O
refer	O
to	O
the	O
IBM	B-Application
i	I-Application
operating	O
system	O
running	O
on	O
modern	O
Power	B-Device
Systems	I-Device
hardware	O
.	O
</s>
<s>
In	O
the	O
early	O
1980s	O
,	O
IBM	O
management	O
became	O
concerned	O
that	O
IBM	O
's	O
large	O
number	O
of	O
incompatible	O
midrange	B-Device
computer	I-Device
systems	O
was	O
hurting	O
the	O
company	O
's	O
competitiveness	O
,	O
particularly	O
against	O
Digital	O
Equipment	O
Corporation	O
's	O
VAX	B-Device
.	O
</s>
<s>
In	O
1982	O
,	O
a	O
project	O
named	O
Fort	O
Knox	O
commenced	O
,	O
which	O
was	O
intended	O
to	O
consolidate	O
the	O
System/36	B-Device
,	O
the	O
System/38	B-Device
,	O
the	O
IBM	B-Device
8100	I-Device
,	O
the	O
Series/1	B-Device
and	O
the	O
IBM	B-Device
4300	I-Device
series	I-Device
into	O
a	O
single	O
product	O
line	O
based	O
around	O
an	O
IBM	O
801-based	O
processor	O
codenamed	O
Iliad	O
,	O
while	O
retaining	O
backwards	O
compatibility	O
with	O
all	O
the	O
systems	O
it	O
was	O
intended	O
to	O
replace	O
.	O
</s>
<s>
As	O
the	O
project	O
advanced	O
,	O
the	O
requirement	O
to	O
support	O
IBM	B-Device
8100	I-Device
and	O
Series/1	B-Device
software	O
was	O
dropped	O
.	O
</s>
<s>
These	O
engineers	O
developed	O
code	O
which	O
allowed	O
System/36	B-Device
applications	O
to	O
run	O
on	O
top	O
of	O
the	O
System/38	B-Device
,	O
and	O
when	O
Fort	O
Knox	O
was	O
cancelled	O
,	O
this	O
skunkworks	O
project	O
evolved	O
into	O
an	O
official	O
project	O
to	O
replace	O
both	O
the	O
System/36	B-Device
and	O
System/38	B-Device
with	O
a	O
single	O
new	O
hardware	O
platform	O
.	O
</s>
<s>
The	O
Silverlake	O
hardware	O
was	O
essentially	O
an	O
evolution	O
of	O
the	O
System/38	B-Device
which	O
reused	O
some	O
of	O
the	O
technology	O
developed	O
for	O
the	O
Fort	O
Knox	O
project	O
.	O
</s>
<s>
Silverlake	O
's	O
goal	O
was	O
to	O
deliver	O
a	O
replacement	O
for	O
the	O
System/36	B-Device
and	O
System/38	B-Device
in	O
as	O
short	O
of	O
a	O
timeframe	O
as	O
possible	O
,	O
as	O
the	O
Fort	O
Knox	O
project	O
had	O
stalled	O
new	O
product	O
development	O
at	O
Rochester	O
,	O
leaving	O
IBM	O
without	O
a	O
competitive	O
midrange	B-Device
system	I-Device
.	O
</s>
<s>
On	O
its	O
launch	O
in	O
1986	O
,	O
the	O
System/370	B-Device
-compatible	O
IBM	B-Device
9370	I-Device
was	O
positioned	O
as	O
IBM	O
's	O
preferred	O
midrange	O
platform	O
,	O
but	O
failed	O
to	O
achieve	O
the	O
commercial	O
success	O
IBM	O
hoped	O
it	O
would	O
have	O
.	O
</s>
<s>
Much	O
like	O
Silverlake	O
,	O
the	O
9370	O
also	O
reused	O
the	O
co-processor	O
developed	O
during	O
the	O
Fort	O
Knox	O
project	O
as	O
its	O
main	O
processor	O
,	O
and	O
the	O
same	O
SPD	O
I/O	O
bus	O
which	O
was	O
derived	O
from	O
the	O
Series/1	B-Device
bus	O
.	O
</s>
<s>
On	O
June	O
21	O
,	O
1988	O
,	O
IBM	O
officially	O
announced	O
the	O
Silverlake	O
system	O
as	O
the	O
Application	B-Device
System/400	I-Device
(	O
AS/400	B-Device
)	O
.	O
</s>
<s>
The	O
AS/400	B-Device
operating	O
system	O
was	O
named	O
Operating	O
System/400	O
(	O
OS/400	B-Application
)	O
.	O
</s>
<s>
The	O
creators	O
of	O
the	O
AS/400	B-Device
originally	O
planned	O
to	O
use	O
the	O
name	O
System/40	O
,	O
but	O
IBM	O
had	O
adopted	O
a	O
new	O
product	O
nomenclature	O
around	O
the	O
same	O
time	O
,	O
which	O
led	O
to	O
the	O
Application	B-Device
System/400	I-Device
name	O
.	O
</s>
<s>
Personal	B-Device
System/2	I-Device
and	O
Enterprise	B-Device
System/9000	I-Device
)	O
.	O
</s>
<s>
PS/2	B-Device
and	O
PS/55	B-Device
)	O
,	O
three	O
digit	O
numbers	O
for	O
midrange	B-Device
systems	I-Device
(	O
e.g.	O
</s>
<s>
AS/400	B-Device
)	O
and	O
four	O
digit	O
numbers	O
for	O
mainframes	O
(	O
e.g.	O
</s>
<s>
ES/9000	B-Device
)	O
.	O
</s>
<s>
The	O
reassignment	O
of	O
two	O
digit	O
model	O
numbers	O
from	O
midrange	B-Device
systems	I-Device
to	O
personal	O
systems	O
was	O
to	O
prevent	O
the	O
personal	O
systems	O
from	O
running	O
out	O
of	O
single-digit	O
numbers	O
for	O
new	O
products	O
.	O
</s>
<s>
In	O
1990	O
,	O
IBM	O
Rochester	O
began	O
work	O
to	O
replace	O
the	O
AS/400	B-Device
'	O
s	O
original	O
System/38	B-Device
-derived	O
48-bit	O
CISC	B-Architecture
processors	I-Architecture
with	O
a	O
96-bit	O
architecture	O
known	O
as	O
C-RISC	O
(	O
Commercial	O
RISC	B-Architecture
)	O
.	O
</s>
<s>
Rather	O
than	O
being	O
a	O
clean-slate	O
design	O
,	O
C-RISC	O
would	O
have	O
added	O
RISC-style	O
and	O
VLIW-style	O
instructions	O
to	O
the	O
AS/400	B-Device
'	O
s	O
processor	O
,	O
while	O
maintaining	O
backwards	O
compatibility	O
with	O
the	O
System/370	B-Device
-style	O
Internal	O
Microprogrammed	O
Interface	O
(	O
IMPI	O
)	O
instruction	B-General_Concept
set	I-General_Concept
and	O
the	O
microcode	B-Device
used	O
to	O
implement	O
it	O
.	O
</s>
<s>
In	O
1991	O
,	O
at	O
the	O
request	O
of	O
IBM	O
president	O
Jack	O
Kuehler	O
,	O
a	O
team	O
under	O
the	O
leadership	O
of	O
Frank	O
Soltis	O
delivered	O
a	O
proposal	O
to	O
adapt	O
the	O
64-bit	B-Device
PowerPC	B-Architecture
architecture	O
to	O
support	O
the	O
needs	O
of	O
the	O
AS/400	B-Device
platform	O
.	O
</s>
<s>
Their	O
extensions	O
to	O
the	O
PowerPC	B-Architecture
architecture	O
,	O
known	O
as	O
Amazon	O
(	O
and	O
later	O
as	O
PowerPC	B-Architecture
AS	O
)	O
,	O
were	O
approved	O
by	O
IBM	O
management	O
instead	O
of	O
the	O
C-RISC	O
design	O
for	O
development	O
into	O
the	O
next	O
AS/400	B-Device
processor	O
architecture	O
.	O
</s>
<s>
IBM	O
initially	O
attempted	O
to	O
create	O
a	O
single	O
PowerPC	B-Architecture
implementation	O
for	O
both	O
AS/400	B-Device
and	O
high-end	O
RS/6000	B-Device
systems	O
known	O
as	O
Belatrix	O
.	O
</s>
<s>
Instead	O
,	O
a	O
pair	O
of	O
AS/400	B-Device
-specific	O
processors	O
were	O
designed	O
at	O
IBM	O
Endicott	O
and	O
IBM	O
Rochester	O
,	O
known	O
as	O
Cobra	O
(	O
for	O
low	O
end	O
systems	O
)	O
and	O
Muskie	O
(	O
for	O
high	O
end	O
systems	O
)	O
respectively	O
.	O
</s>
<s>
These	O
became	O
the	O
initial	O
implementations	O
of	O
the	O
IBM	B-Device
RS64	I-Device
processor	O
line	O
.	O
</s>
<s>
The	O
RS64	B-Device
series	O
continued	O
to	O
be	O
developed	O
as	O
a	O
separate	O
product	O
line	O
at	O
IBM	O
until	O
the	O
POWER4	B-Device
merged	O
both	O
the	O
RS64	B-Device
and	O
POWER	B-Device
product	O
lines	O
together	O
.	O
</s>
<s>
Despite	O
the	O
move	O
from	O
IMPI	O
to	O
an	O
entirely	O
different	O
processor	O
architecture	O
,	O
the	O
AS/400	B-Device
'	O
s	O
Technology	O
Independent	O
Machine	O
Interface	O
(	O
TIMI	O
)	O
mostly	O
hid	O
the	O
changes	O
from	O
users	O
and	O
applications	O
,	O
and	O
transparently	O
recompiled	O
applications	O
for	O
the	O
new	O
processor	O
architecture	O
.	O
</s>
<s>
The	O
port	O
of	O
OS/400	B-Application
to	O
the	O
PowerPC	B-Architecture
AS	O
architecture	O
required	O
a	O
rewrite	O
of	O
most	O
of	O
the	O
code	O
below	O
the	O
TIMI	O
due	O
to	O
the	O
use	O
of	O
IMPI	O
microcode	B-Device
to	O
implement	O
significant	O
quantities	O
of	O
the	O
operating	O
system	O
's	O
low	O
level	O
code	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
creation	O
of	O
the	O
System	O
Licensed	O
Internal	O
Code	O
(	O
SLIC	O
)	O
-	O
a	O
new	O
implementation	O
of	O
the	O
lower	O
levels	O
of	O
the	O
operating	O
system	O
mostly	O
written	O
in	O
C++	B-Language
.	O
</s>
<s>
The	O
AS/400	B-Device
family	O
line	O
was	O
rebranded	O
several	O
times	O
in	O
the	O
1990s	O
and	O
2000s	O
as	O
IBM	O
introduced	O
newer	O
generations	O
of	O
hardware	O
and	O
operating	O
system	O
.	O
</s>
<s>
In	O
1994	O
,	O
the	O
AS/400	B-Device
Advanced	O
Series	O
name	O
was	O
used	O
for	O
new	O
models	O
,	O
followed	O
by	O
the	O
rebranding	O
of	O
the	O
product	O
line	O
to	O
AS/400e	O
(	O
the	O
e	O
standing	O
for	O
e-business	B-Application
)	O
in	O
1997	O
.	O
</s>
<s>
In	O
2000	O
,	O
eServer	B-Device
iSeries	I-Device
was	O
introduced	O
as	O
part	O
of	O
its	O
eServer	B-Application
branding	I-Application
initiative	I-Application
.	O
</s>
<s>
The	O
eServer	B-Device
iSeries	I-Device
was	O
built	O
on	O
the	O
POWER4	B-Device
processor	O
from	O
the	O
RS64	B-Device
processors	O
used	O
by	O
previous	O
generations	O
,	O
meaning	O
that	O
the	O
same	O
processors	O
were	O
used	O
in	O
both	O
the	O
iSeries	B-Device
and	O
pSeries	O
platforms	O
,	O
the	O
latter	O
of	O
which	O
ran	O
AIX	B-Application
.	O
</s>
<s>
Successive	O
generations	O
of	O
iSeries	B-Device
and	O
pSeries	O
hardware	O
converged	O
until	O
they	O
were	O
essentially	O
the	O
same	O
hardware	O
sold	O
under	O
different	O
names	O
and	O
with	O
different	O
operating	O
systems	O
.	O
</s>
<s>
In	O
2004	O
,	O
eServer	B-Application
i5	O
(	O
along	O
with	O
OS/400	B-Application
becoming	O
i5/OS	B-Application
)	O
the	O
5	O
signifying	O
the	O
use	O
of	O
POWER5	B-Device
processors	O
,	O
was	O
introduced	O
,	O
replacing	O
the	O
eServer	B-Device
iSeries	I-Device
brand	O
..	O
</s>
<s>
The	O
final	O
rebranding	O
occurred	O
in	O
2006	O
,	O
when	O
IBM	O
rebranded	O
the	O
eServer	B-Application
i5	O
to	O
System	O
i	O
.	O
</s>
<s>
In	O
April	O
2008	O
,	O
IBM	O
introduced	O
the	O
IBM	B-Device
Power	I-Device
Systems	I-Device
line	O
,	O
which	O
was	O
a	O
convergence	O
of	O
System	O
i	O
and	O
System	B-Device
p	I-Device
product	O
lines	O
.	O
</s>
<s>
The	O
first	O
Power	B-Device
Systems	I-Device
machines	O
used	O
the	O
POWER6	B-Device
processors	O
;	O
i5/OS	B-Application
was	O
renamed	O
as	O
IBM	B-Application
i	I-Application
,	O
in	O
order	O
to	O
remove	O
the	O
association	O
with	O
POWER5	B-Device
processors	O
.	O
</s>
<s>
IBM	B-Application
i	I-Application
is	O
sold	O
as	O
one	O
of	O
the	O
operating	O
system	O
options	O
for	O
Power	B-Device
Systems	I-Device
(	O
along	O
with	O
AIX	B-Application
and	O
Linux	B-Application
)	O
instead	O
of	O
being	O
tied	O
to	O
its	O
own	O
hardware	O
platform	O
.	O
</s>
<s>
Although	O
announced	O
in	O
1988	O
,	O
the	O
AS/400	B-Device
remains	O
IBM	O
's	O
most	O
recent	O
major	O
architectural	O
shift	O
that	O
was	O
developed	O
wholly	O
internally	O
.	O
</s>
<s>
Instead	O
,	O
IBM	O
now	O
prefers	O
to	O
make	O
key	O
product	O
strides	O
through	O
acquisition	O
(	O
e.g.	O
,	O
the	O
takeovers	O
of	O
Lotus	O
Software	O
and	O
Rational	O
Software	O
)	O
and	O
to	O
support	O
the	O
development	O
of	O
open	O
standards	O
,	O
particularly	O
Linux	B-Application
.	O
</s>
<s>
After	O
the	O
departure	O
of	O
CEO	O
John	O
Akers	O
in	O
1993	O
,	O
when	O
IBM	O
looked	O
likely	O
to	O
be	O
split	O
up	O
,	O
Bill	O
Gates	O
commented	O
that	O
the	O
only	O
part	O
of	O
IBM	O
that	O
Microsoft	O
would	O
be	O
interested	O
in	O
was	O
the	O
AS/400	B-Device
division	O
.	O
</s>
<s>
(	O
At	O
the	O
time	O
,	O
many	O
of	O
Microsoft	O
's	O
business	O
and	O
financial	O
systems	O
ran	O
on	O
the	O
AS/400	B-Device
platform	O
,	O
something	O
that	O
ceased	O
to	O
be	O
the	O
case	O
around	O
1999	O
,	O
with	O
the	O
introduction	O
of	O
Windows	B-Application
2000	I-Application
.	O
)	O
</s>
<s>
According	O
to	O
Frank	O
Soltis	O
,	O
one	O
of	O
the	O
architects	O
of	O
the	O
AS/400	B-Device
platform	O
,	O
the	O
AS/400	B-Device
'	O
s	O
architecture	O
is	O
defined	O
by	O
five	O
architectural	O
principles	O
.	O
</s>
<s>
Most	O
of	O
these	O
principles	O
are	O
inherited	O
from	O
System/38	B-Device
.	O
</s>
<s>
The	O
high-level	O
instruction	B-General_Concept
set	I-General_Concept
(	O
called	O
TIMI	O
for	O
"	O
Technology	O
Independent	O
Machine	O
Interface	O
"	O
by	O
IBM	O
)	O
,	O
allows	O
application	B-Application
programs	I-Application
to	O
take	O
advantage	O
of	O
advances	O
in	O
hardware	O
and	O
software	O
without	O
recompilation	O
.	O
</s>
<s>
TIMI	O
is	O
a	O
virtual	B-Language
instruction	I-Language
set	I-Language
independent	O
of	O
the	O
underlying	O
machine	B-Language
instruction	I-Language
set	O
of	O
the	O
CPU	O
.	O
</s>
<s>
User-mode	O
programs	O
contain	O
both	O
TIMI	O
instructions	O
and	O
the	O
machine	B-Language
instructions	I-Language
of	O
the	O
CPU	O
,	O
thus	O
ensuring	O
hardware	O
independence	O
.	O
</s>
<s>
This	O
is	O
conceptually	O
somewhat	O
similar	O
to	O
the	O
virtual	B-Architecture
machine	I-Architecture
architecture	O
of	O
programming	O
environments	O
such	O
as	O
Java	B-Language
and	O
.NET	B-Application
.	O
</s>
<s>
Unlike	O
some	O
other	O
virtual-machine	O
architectures	O
in	O
which	O
the	O
virtual	O
instructions	O
are	O
interpreted	O
at	O
run	B-Library
time	I-Library
,	O
TIMI	O
instructions	O
are	O
never	O
interpreted	O
.	O
</s>
<s>
They	O
constitute	O
an	O
intermediate	O
compile	B-Application
time	I-Application
step	O
and	O
are	O
translated	O
into	O
the	O
processor	O
's	O
instruction	B-General_Concept
set	I-General_Concept
as	O
the	O
final	O
compilation	O
step	O
.	O
</s>
<s>
The	O
TIMI	O
instructions	O
are	O
stored	O
within	O
the	O
final	O
program	O
object	O
,	O
in	O
addition	O
to	O
the	O
executable	O
machine	B-Language
instructions	I-Language
.	O
</s>
<s>
This	O
is	O
how	O
application	O
objects	O
compiled	O
on	O
one	O
processor	O
family	O
(	O
e.g.	O
,	O
the	O
original	O
CISC	B-Architecture
AS/400	B-Device
48-bit	O
processors	O
)	O
could	O
be	O
moved	O
to	O
a	O
new	O
processor	O
(	O
e.g.	O
,	O
PowerPC	B-Architecture
64-bit	B-Device
)	O
without	O
re-compilation	O
.	O
</s>
<s>
An	O
application	O
saved	O
from	O
the	O
older	O
48-bit	O
platform	O
can	O
simply	O
be	O
restored	O
onto	O
the	O
new	O
64-bit	B-Device
platform	O
where	O
the	O
operating	O
system	O
discards	O
the	O
old	O
machine	B-Language
instructions	I-Language
and	O
re-translates	O
the	O
TIMI	O
instructions	O
into	O
64-bit	B-Device
instructions	O
for	O
the	O
new	O
processor	O
.	O
</s>
<s>
The	O
system	O
's	O
instruction	B-General_Concept
set	I-General_Concept
defines	O
all	O
pointers	O
as	O
128-bit	O
.	O
</s>
<s>
This	O
was	O
the	O
original	O
design	O
feature	O
of	O
the	O
System/38	B-Device
(	O
S/38	B-Device
)	O
in	O
the	O
mid	O
1970s	O
planning	O
for	O
future	O
use	O
of	O
faster	O
processors	O
,	O
memory	O
and	O
an	O
expanded	O
address	O
space	O
.	O
</s>
<s>
The	O
original	O
AS/400	B-Device
CISC	B-Architecture
models	O
used	O
the	O
same	O
48-bit	O
address	O
space	O
as	O
the	O
S/38	B-Device
.	O
</s>
<s>
The	O
address	O
space	O
was	O
expanded	O
in	O
1995	O
when	O
the	O
RISC	B-Architecture
PowerPC	B-Architecture
RS64	B-Device
64-bit	B-Device
CPU	I-Device
processor	O
replaced	O
the	O
48-bit	O
CISC	B-Architecture
processor	I-Architecture
.	O
</s>
<s>
OS/400	B-Application
(	O
now	O
known	O
as	O
IBM	B-Application
i	I-Application
)	O
is	O
the	O
native	O
operating	O
system	O
of	O
the	O
AS/400	B-Device
platform	O
,	O
and	O
was	O
the	O
sole	O
operating	O
system	O
supported	O
on	O
the	O
original	O
AS/400	B-Device
hardware	O
.	O
</s>
<s>
Many	O
of	O
the	O
advanced	O
features	O
associated	O
with	O
the	O
AS/400	B-Device
are	O
implemented	O
in	O
the	O
operating	O
system	O
as	O
opposed	O
to	O
the	O
underlying	O
hardware	O
,	O
which	O
changed	O
significantly	O
throughout	O
the	O
life	O
of	O
the	O
AS/400	B-Device
platform	O
.	O
</s>
<s>
Features	O
include	O
a	O
RDBMS	B-Application
(	O
Db2	B-Application
for	I-Application
i	I-Application
)	O
,	O
a	O
menu-driven	O
interface	O
,	O
support	O
for	O
multiple	O
users	O
,	O
block-oriented	O
terminal	O
support	O
(	O
IBM	B-Device
5250	I-Device
)	O
,	O
and	O
printers	O
.	O
</s>
<s>
Unlike	O
the	O
"	O
everything	B-Application
is	I-Application
a	I-Application
file	I-Application
"	O
feature	O
of	O
Unix	B-Application
and	O
its	B-Operating_System
derivatives	I-Operating_System
,	O
on	O
IBM	B-Application
i	I-Application
everything	O
is	O
an	O
object	O
(	O
with	O
built-in	O
persistence	O
and	O
garbage	O
collection	O
)	O
.	O
</s>
<s>
IBM	O
uses	O
a	O
single-level	B-Device
store	I-Device
virtual	O
memory	O
architecture	O
in	O
the	O
AS/400	B-Device
platform	O
.	O
</s>
<s>
For	O
64-bit	B-Device
PowerPC	B-Architecture
processors	I-Architecture
,	O
the	O
virtual	O
address	O
resides	O
in	O
the	O
rightmost	O
64	B-Device
bits	I-Device
of	O
a	O
pointer	O
while	O
it	O
was	O
48	O
bits	O
in	O
the	O
S/38	B-Device
and	O
CISC	B-Architecture
AS/400	B-Device
.	O
</s>
<s>
The	O
64-bit	B-Device
address	O
space	O
references	O
main	O
memory	O
and	O
disk	O
as	O
a	O
single	O
address	O
set	O
which	O
is	O
the	O
single-level	B-Device
store	I-Device
concept	O
.	O
</s>
<s>
Later	O
generations	O
of	O
hardware	O
are	O
also	O
capable	O
of	O
supporting	O
various	O
guest	O
operating	O
systems	O
,	O
including	O
SSP	B-Operating_System
,	O
AIX	B-Application
,	O
Linux	B-Application
,	O
Microsoft	B-Application
Windows	I-Application
2000	I-Application
and	O
Windows	B-Application
Server	I-Application
2003	I-Application
.	O
</s>
<s>
While	O
OS/400	B-Application
,	O
AIX	B-Application
,	O
and	O
Linux	B-Application
are	O
supported	O
on	O
the	O
POWER	B-Device
processors	O
on	O
LPARs	B-Device
(	O
logical	B-Device
partitions	I-Device
)	O
,	O
Windows	O
is	O
supported	O
with	O
either	O
single-processor	O
internal	O
blade	O
servers	O
(	O
IXS	O
)	O
or	O
externally	O
linked	O
multiple-processor	O
servers	O
(	O
IXA	O
and	O
iSCSI	O
)	O
.	O
</s>
<s>
SSP	B-Operating_System
guests	O
were	O
supported	O
using	O
emulation	O
from	O
OS/400	B-Application
V3R6	O
through	O
V4R4	O
using	O
the	O
Advanced	O
36	O
Machine	O
facility	O
of	O
the	O
operating	O
system	O
,	O
a	O
feature	O
distinct	O
from	O
the	O
System/36	B-Device
Environment	O
compatibility	O
layer	O
which	O
requires	O
System/36	B-Device
software	O
to	O
be	O
recompiled	O
.	O
</s>
