<s>
Power	B-Architecture
ISA	I-Architecture
is	O
a	O
reduced	B-Architecture
instruction	I-Architecture
set	I-Architecture
computer	I-Architecture
(	O
RISC	B-Architecture
)	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
currently	O
developed	O
by	O
the	O
OpenPOWER	B-Application
Foundation	I-Application
,	O
led	O
by	O
IBM	O
.	O
</s>
<s>
Power	B-Architecture
ISA	I-Architecture
is	O
an	O
evolution	O
of	O
the	O
PowerPC	B-Architecture
ISA	O
,	O
created	O
by	O
the	O
mergers	O
of	O
the	O
core	O
PowerPC	B-Architecture
ISA	O
and	O
the	O
optional	O
Book	O
E	O
for	O
embedded	O
applications	O
.	O
</s>
<s>
Different	O
classes	O
of	O
processors	O
are	O
required	O
to	O
implement	O
certain	O
categories	O
,	O
for	O
example	O
a	O
server-class	O
processor	O
includes	O
the	O
categories	O
:	O
Base	O
,	O
Server	O
,	O
Floating-Point	O
,	O
64-Bit	B-Device
,	O
etc	O
.	O
</s>
<s>
Power	B-Architecture
ISA	I-Architecture
is	O
a	O
RISC	B-Architecture
load/store	B-Architecture
architecture	I-Architecture
.	O
</s>
<s>
It	O
has	O
multiple	O
sets	O
of	O
registers	B-General_Concept
:	O
</s>
<s>
32	O
×	O
32-bit	O
or	O
64-bit	B-Device
general-purpose	O
registers	B-General_Concept
(	O
GPRs	B-General_Concept
)	O
for	O
integer	B-General_Concept
operations	I-General_Concept
.	O
</s>
<s>
64	O
×	O
128-bit	O
vector	O
scalar	O
registers	B-General_Concept
(	O
VSRs	O
)	O
for	O
vector	B-Operating_System
operations	I-Operating_System
and	O
floating-point	B-General_Concept
operations	I-General_Concept
.	O
</s>
<s>
32	O
×	O
64-bit	B-Device
floating-point	O
registers	B-General_Concept
(	O
FPRs	O
)	O
as	O
part	O
of	O
the	O
VSRs	O
for	O
floating-point	B-General_Concept
operations	I-General_Concept
.	O
</s>
<s>
32	O
×	O
128-bit	O
vector	O
registers	B-General_Concept
(	O
VRs	O
)	O
as	O
part	O
of	O
the	O
VSRs	O
for	O
vector	B-Operating_System
operations	I-Operating_System
.	O
</s>
<s>
11	O
special	O
registers	B-General_Concept
of	O
various	O
sizes	O
:	O
Counter	O
Register	O
(	O
CTR	O
)	O
,	O
link	O
register	O
(	O
LR	O
)	O
,	O
time	O
base	O
(	O
TBU	O
,	O
TBL	O
)	O
,	O
alternate	O
time	O
base	O
(	O
ATBU	O
,	O
ATBL	O
)	O
,	O
accumulator	O
(	O
ACC	O
)	O
,	O
status	B-General_Concept
registers	I-General_Concept
(	O
XER	O
,	O
FPSCR	O
,	O
VSCR	O
,	O
SPEFSCR	O
)	O
.	O
</s>
<s>
Instructions	O
up	O
to	O
version	O
3.0	O
have	O
a	O
length	O
of	O
32	O
bits	O
,	O
with	O
the	O
exception	O
of	O
the	O
VLE	O
(	O
variable-length	O
encoding	O
)	O
subset	O
that	O
provides	O
for	O
higher	O
code	O
density	O
for	O
low-end	O
embedded	O
applications	O
,	O
and	O
version	O
3.1	O
which	O
introduced	O
prefixing	O
to	O
create	O
64-bit	B-Device
instructions	O
.	O
</s>
<s>
Most	O
instructions	O
are	O
triadic	B-Algorithm
,	O
i.e.	O
</s>
<s>
Single	O
-	O
and	O
double-precision	O
IEEE-754	O
compliant	O
floating-point	B-General_Concept
operations	I-General_Concept
are	O
supported	O
,	O
including	O
additional	O
fused	O
multiply	O
–	O
add	O
(	O
FMA	O
)	O
and	O
decimal	O
floating-point	O
instructions	O
.	O
</s>
<s>
There	O
are	O
provisions	O
for	O
single	B-Device
instruction	I-Device
,	I-Device
multiple	I-Device
data	I-Device
(	O
SIMD	B-Device
)	O
operations	O
on	O
integer	O
and	O
floating-point	O
data	O
on	O
up	O
to	O
16	O
elements	O
in	O
one	O
instruction	O
.	O
</s>
<s>
Power	B-Architecture
ISA	I-Architecture
has	O
support	O
for	O
Harvard	B-Device
cache	B-General_Concept
,	O
i.e.	O
</s>
<s>
Memory	O
operations	O
are	O
strictly	O
load/store	O
,	O
but	O
allow	O
for	O
out-of-order	B-General_Concept
execution	I-General_Concept
.	O
</s>
<s>
There	O
is	O
also	O
support	O
for	O
both	O
big	O
and	O
little-endian	O
addressing	O
with	O
separate	O
categories	O
for	O
moded	O
and	O
per-page	O
endianness	O
,	O
and	O
support	O
for	O
both	O
32-bit	O
and	O
64-bit	B-Device
addressing	O
.	O
</s>
<s>
Different	O
modes	O
of	O
operation	O
include	O
user	O
,	O
supervisor	O
and	O
hypervisor	B-Operating_System
.	O
</s>
<s>
Misc	O
–	O
floating	O
point	O
,	O
vector	O
,	O
signal	O
processing	O
,	O
cache	B-General_Concept
locking	O
,	O
decimal	O
floating	O
point	O
,	O
etc	O
.	O
</s>
<s>
The	O
Power	B-Architecture
ISA	I-Architecture
specification	O
is	O
divided	O
into	O
five	O
parts	O
,	O
called	O
"	O
books	O
"	O
:	O
</s>
<s>
Book	O
I	O
–	O
User	O
Instruction	B-General_Concept
Set	I-General_Concept
Architecture	I-General_Concept
covers	O
the	O
base	O
instruction	B-General_Concept
set	I-General_Concept
available	O
to	O
the	O
application	O
programmer	O
.	O
</s>
<s>
It	O
includes	O
chapters	O
regarding	O
auxiliary	O
processing	O
units	O
like	O
digital	B-Architecture
signal	I-Architecture
processors	I-Architecture
(	O
DSPs	B-Architecture
)	O
and	O
the	O
AltiVec	B-General_Concept
extension	O
.	O
</s>
<s>
Book	O
II	O
–	O
Virtual	O
Environment	O
Architecture	O
defines	O
the	O
storage	O
model	O
available	O
to	O
the	O
application	O
programmer	O
,	O
including	O
timing	O
,	O
synchronization	O
,	O
cache	B-General_Concept
management	O
,	O
storage	O
features	O
,	O
byte	B-Application
ordering	O
.	O
</s>
<s>
It	O
is	O
mainly	O
the	O
contents	O
of	O
the	O
Book	O
III	O
of	O
the	O
former	O
PowerPC	B-Architecture
ISA	O
.	O
</s>
<s>
It	O
is	O
derived	O
from	O
the	O
former	O
PowerPC	B-Architecture
Book	O
E	O
.	O
</s>
<s>
They	O
use	O
16-bit	O
instructions	O
and	O
big-endian	O
byte	B-Application
ordering	O
.	O
</s>
<s>
New	O
in	O
version	O
3	O
of	O
the	O
Power	B-Architecture
ISA	I-Architecture
is	O
that	O
you	O
do	O
n't	O
have	O
to	O
implement	O
the	O
entire	O
specification	O
to	O
be	O
compliant	O
.	O
</s>
<s>
The	O
sprawl	O
of	O
instructions	O
and	O
technologies	O
has	O
made	O
the	O
complete	O
specification	O
unwieldy	O
,	O
so	O
the	O
OpenPOWER	B-Application
Foundation	I-Application
have	O
decided	O
to	O
enabled	O
tiered	O
compliancy	O
.	O
</s>
<s>
This	O
is	O
explained	O
in	O
the	O
OpenPOWER	B-Application
EULA	O
.	O
</s>
<s>
Basic	O
fixed	O
point	O
and	O
load/store	B-General_Concept
instructions	I-General_Concept
,	O
which	O
is	O
really	O
the	O
Base	O
architecture	O
.	O
</s>
<s>
Adding	O
floating-point	B-General_Concept
operations	I-General_Concept
to	O
the	O
Base	O
.	O
</s>
<s>
Intended	O
for	O
server	O
grade	O
Linux	O
,	O
adding	O
features	O
like	O
64-bit	B-Device
,	O
optional	O
SIMD/VSX	O
,	O
Radix	O
MMU	O
,	O
little-endian	O
mode	O
and	O
hypervisor	B-Operating_System
support	O
.	O
</s>
<s>
ACS	O
–	O
AIX	B-Application
Compliancy	O
Subset	O
.	O
</s>
<s>
Intended	O
to	O
run	O
AIX	B-Application
,	O
adding	O
features	O
like	O
decimal	O
and	O
quad-precision	O
floating	O
point	O
,	O
big-endian	O
mode	O
and	O
symmetric	O
multiprocessing	O
.	O
</s>
<s>
If	O
the	O
extension	O
is	O
general-purpose	O
enough	O
,	O
the	O
OpenPOWER	B-Application
Foundation	I-Application
asks	O
that	O
implementors	O
submit	O
it	O
as	O
a	O
Request	O
for	O
Comments	O
(	O
RFC	O
)	O
to	O
the	O
.	O
</s>
<s>
Note	O
that	O
it	O
is	O
not	O
strictly	O
necessary	O
to	O
join	O
the	O
OpenPOWER	B-Application
Foundation	I-Application
to	O
submit	O
RFCs	O
.	O
</s>
<s>
Regarding	O
the	O
Linux	O
Compliancy	O
subset	O
having	O
VSX	O
(	O
SIMD	B-Device
)	O
optional	O
:	O
in	O
2003	O
–	O
4	O
,	O
64-bit	B-Device
EABI	O
v1.9	O
made	O
SIMD	B-Device
optional	O
,	O
but	O
in	O
July	O
2015	O
,	O
to	O
improve	O
performance	O
for	O
IBM	O
POWER9	B-Device
systems	O
,	O
SIMD	B-Device
was	O
made	O
mandatory	O
in	O
EABI	O
v2.0	O
.	O
</s>
<s>
This	O
discrepancy	O
between	O
SIMD	B-Device
being	O
optional	O
in	O
the	O
Linux	O
Compliancy	O
level	O
but	O
mandatory	O
in	O
EABI	O
v2.0	O
cannot	O
be	O
rectified	O
without	O
considerable	O
effort	O
:	O
backwards	O
incompatibility	O
for	O
Linux	O
distributions	O
is	O
not	O
a	O
viable	O
option	O
.	O
</s>
<s>
At	O
present	O
this	O
leaves	O
new	O
OpenPOWER	B-Application
implementors	O
wishing	O
to	O
run	O
standard	O
Linux	O
distributions	O
having	O
to	O
implement	O
a	O
massive	O
962	O
instructions	O
.	O
</s>
<s>
By	O
contrast	O
,	O
RISC-V	O
RV64GC	O
,	O
the	O
minimum	O
to	O
run	O
Linux	O
,	O
requires	O
only	O
165	O
.	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.2.03	O
is	O
based	O
on	O
the	O
former	O
PowerPC	B-Architecture
ISA	O
v.2.02	O
in	O
POWER5+	O
and	O
the	O
Book	O
E	O
extension	O
of	O
the	O
PowerPC	B-Architecture
specification	O
.	O
</s>
<s>
The	O
Book	O
I	O
included	O
five	O
new	O
chapters	O
regarding	O
auxiliary	O
processing	O
units	O
like	O
DSPs	B-Architecture
and	O
the	O
AltiVec	B-General_Concept
extension	O
.	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.2.04	O
was	O
finalized	O
in	O
June	O
2007	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
Power	B-Architecture
ISA	I-Architecture
v.2.03	O
and	O
includes	O
changes	O
primarily	O
to	O
the	O
Book	O
III-S	O
part	O
regarding	O
virtualization	B-General_Concept
,	O
hypervisor	B-Operating_System
functions	O
,	O
logical	B-Device
partitioning	I-Device
and	O
virtual	B-General_Concept
page	I-General_Concept
handling	O
.	O
</s>
<s>
The	O
PA6T	B-General_Concept
core	O
from	O
P.A.	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.2.05	O
was	O
released	O
in	O
December	O
2007	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
Power	B-Architecture
ISA	I-Architecture
v.2.04	O
and	O
includes	O
changes	O
primarily	O
to	O
Book	O
I	O
and	O
Book	O
III-S	O
,	O
including	O
significant	O
enhancements	O
such	O
as	O
decimal	O
arithmetic	O
(	O
Category	O
:	O
Decimal	O
Floating-Point	O
in	O
Book	O
I	O
)	O
and	O
server	O
hypervisor	B-Operating_System
improvements	O
.	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.2.06	O
was	O
released	O
in	O
February	O
2009	O
,	O
and	O
revised	O
in	O
July	O
2010	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
Power	B-Architecture
ISA	I-Architecture
v.2.05	O
and	O
includes	O
extensions	O
for	O
the	O
POWER7	B-Device
processor	O
and	O
e500-mc	O
core	O
.	O
</s>
<s>
Book	O
III-E	O
also	O
includes	O
significant	O
enhancement	O
for	O
the	O
embedded	O
specification	O
regarding	O
hypervisor	B-Operating_System
and	O
virtualisation	O
on	O
single	O
and	O
multi	O
core	O
implementations	O
.	O
</s>
<s>
The	O
spec	O
was	O
revised	O
in	O
November	O
2010	O
to	O
the	O
Power	B-Architecture
ISA	I-Architecture
v.2.06	O
revision	O
B	O
spec	O
,	O
enhancing	O
virtualization	B-General_Concept
features	O
.	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.2.07	O
was	O
released	O
in	O
May	O
2013	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
Power	B-Architecture
ISA	I-Architecture
v.2.06	O
and	O
includes	O
major	O
enhancements	O
to	O
logical	B-Device
partition	I-Device
functions	I-Device
,	O
transactional	B-Operating_System
memory	I-Operating_System
,	O
expanded	O
performance	O
monitoring	O
,	O
new	O
storage	O
control	O
features	O
,	O
additions	O
to	O
the	O
VMX	O
and	O
VSX	O
vector	B-Operating_System
facilities	I-Operating_System
(	O
VSX-2	O
)	O
,	O
along	O
with	O
AES	B-Algorithm
and	O
Galois	B-Algorithm
Counter	I-Algorithm
Mode	I-Algorithm
(	O
GCM	O
)	O
,	O
SHA-224	B-Algorithm
,	O
SHA-256	B-Algorithm
,	O
SHA-384	B-Algorithm
and	O
SHA-512	B-Algorithm
(	O
SHA-2	B-Algorithm
)	O
cryptographic	O
extensions	O
and	O
cyclic	O
redundancy	O
check	O
(	O
CRC	O
)	O
algorithms	O
.	O
</s>
<s>
The	O
spec	O
was	O
revised	O
in	O
April	O
2015	O
to	O
the	O
Power	B-Architecture
ISA	I-Architecture
v.2.07	O
B	O
spec	O
.	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.3.0	O
was	O
released	O
in	O
November	O
2015	O
.	O
</s>
<s>
It	O
is	O
the	O
first	O
to	O
come	O
out	O
after	O
the	O
founding	O
of	O
the	O
OpenPOWER	B-Application
Foundation	I-Application
and	O
includes	O
enhancements	O
for	O
a	O
broad	O
spectrum	O
of	O
workloads	O
and	O
removes	O
the	O
server	O
and	O
embedded	O
categories	O
while	O
retaining	O
backwards	O
compatibility	O
and	O
adds	O
support	O
for	O
VSX-3	O
instructions	O
.	O
</s>
<s>
New	O
functions	O
include	O
128-bit	O
quad-precision	O
floating-point	B-General_Concept
operations	I-General_Concept
,	O
a	O
random	O
number	O
generator	O
,	O
hardware-assisted	O
garbage	B-General_Concept
collection	I-General_Concept
and	O
hardware-enforced	O
trusted	O
computing	O
.	O
</s>
<s>
The	O
spec	O
was	O
revised	O
in	O
March	O
2017	O
to	O
the	O
Power	B-Architecture
ISA	I-Architecture
v.3.0	O
B	O
spec	O
,	O
</s>
<s>
The	O
specification	O
for	O
Power	B-Architecture
ISA	I-Architecture
v.3.1	O
was	O
released	O
in	O
May	O
2020	O
.	O
</s>
<s>
Mainly	O
giving	O
support	O
for	O
new	O
functions	O
introduced	O
in	O
Power10	B-Operating_System
,	O
but	O
also	O
includes	O
the	O
notion	O
of	O
optionality	O
to	O
the	O
PowerISA	O
specification	O
.	O
</s>
<s>
Instructions	O
can	O
now	O
be	O
eight	O
bytes	B-Application
long	O
,	O
"	O
prefixed	O
instructions	O
"	O
,	O
compared	O
to	O
the	O
usual	O
four	O
byte	B-Application
"	O
word	O
instructions	O
"	O
.	O
</s>
<s>
A	O
lot	O
of	O
new	O
functions	O
to	O
SIMD	B-Device
and	O
VSX	O
instructions	O
are	O
also	O
added	O
.	O
</s>
<s>
One	O
key	O
benefit	O
of	O
the	O
new	O
64-bit	B-Device
prefixed	O
instructions	O
is	O
the	O
extension	O
of	O
immediates	O
in	O
branches	O
to	O
34-bit	O
.	O
</s>
<s>
The	O
spec	O
was	O
revised	O
in	O
September	O
2021	O
to	O
the	O
Power	B-Architecture
ISA	I-Architecture
v.3.1B	O
spec	O
.	O
</s>
