<s>
M.2	B-Protocol
,	O
pronounced	O
m	O
dot	O
two	O
and	O
formerly	O
known	O
as	O
the	O
Next	B-Protocol
Generation	I-Protocol
Form	I-Protocol
Factor	I-Protocol
(	O
NGFF	B-Protocol
)	O
,	O
is	O
a	B-General_Concept
specification	O
for	O
internally	O
mounted	O
computer	O
expansion	B-Device
cards	I-Device
and	O
associated	O
connectors	O
.	O
</s>
<s>
M.2	B-Protocol
replaces	O
the	O
mSATA	O
standard	O
,	O
which	O
uses	O
the	O
PCI	O
Express	O
Mini	O
Card	O
physical	O
card	O
layout	O
and	O
connectors	O
.	O
</s>
<s>
Employing	O
a	B-General_Concept
more	O
flexible	O
physical	O
specification	O
,	O
M.2	B-Protocol
allows	O
different	O
module	O
widths	O
and	O
lengths	O
,	O
which	O
,	O
paired	O
with	O
the	O
availability	O
of	O
more	O
advanced	O
interfacing	B-Application
features	O
,	O
makes	O
M.2	B-Protocol
more	O
suitable	O
than	O
mSATA	O
in	O
general	O
for	O
solid-state	B-Device
storage	I-Device
applications	O
,	O
particularly	O
in	O
smaller	O
devices	O
such	O
as	O
ultrabooks	B-Device
and	O
tablets	B-Device
.	O
</s>
<s>
Computer	B-General_Concept
bus	I-General_Concept
interfaces	B-Application
provided	O
through	O
the	O
M.2	B-Protocol
connector	O
are	O
PCI	O
Express	O
x4	O
(	O
up	O
to	O
four	O
lanes	O
)	O
,	O
Serial	O
ATA	O
3.0	O
,	O
and	O
USB	B-Protocol
3.0	O
(	O
a	B-General_Concept
single	O
logical	O
port	O
for	O
each	O
of	O
the	O
latter	O
two	O
)	O
.	O
</s>
<s>
It	O
is	O
up	O
to	O
the	O
manufacturer	O
of	O
the	O
M.2	B-Protocol
host	O
or	O
module	O
to	O
select	O
which	O
interfaces	B-Application
are	O
to	O
be	O
supported	O
,	O
depending	O
on	O
the	O
desired	O
level	O
of	O
host	O
support	O
and	O
the	O
module	O
type	O
.	O
</s>
<s>
Different	O
M.2	B-Protocol
connector	O
keying	O
notches	O
denote	O
various	O
purposes	O
and	O
capabilities	O
of	O
both	O
the	O
M.2	B-Protocol
hosts	O
and	O
modules	O
,	O
and	O
also	O
prevent	O
the	O
M.2	B-Protocol
modules	O
from	O
being	O
inserted	O
into	O
incompatible	O
host	O
connectors	O
.	O
</s>
<s>
The	O
M.2	B-Protocol
specification	O
supports	O
NVM	B-Application
Express	I-Application
(	O
NVMe	B-Application
)	O
as	O
the	O
logical	O
device	O
interface	O
for	O
M.2	B-Protocol
PCI	O
Express	O
SSDs	B-Device
,	O
in	O
addition	O
to	O
supporting	O
legacy	B-Device
Advanced	O
Host	B-Application
Controller	I-Application
Interface	I-Application
(	O
AHCI	O
)	O
at	O
the	O
logical	O
interface	O
level	O
.	O
</s>
<s>
While	O
the	O
support	O
for	O
AHCI	O
ensures	O
software-level	O
backward	B-General_Concept
compatibility	I-General_Concept
with	O
legacy	B-Device
SATA	O
devices	O
and	O
legacy	B-Device
operating	B-General_Concept
systems	I-General_Concept
,	O
NVM	B-Application
Express	I-Application
is	O
designed	O
to	O
fully	O
utilize	O
the	O
capability	O
of	O
high-speed	O
PCI	O
Express	O
storage	O
devices	O
to	O
perform	O
many	O
I/O	B-General_Concept
operations	I-General_Concept
in	B-Operating_System
parallel	I-Operating_System
.	O
</s>
<s>
M.2	B-Protocol
modules	O
can	O
integrate	O
multiple	O
functions	O
,	O
including	O
the	O
following	O
device	O
classes	O
:	O
Wi-Fi	O
,	O
Bluetooth	B-Protocol
,	O
satellite	O
navigation	O
,	O
near	O
field	O
communication	O
(	O
NFC	O
)	O
,	O
digital	O
radio	O
,	O
WiGig	O
,	O
wireless	B-General_Concept
WAN	I-General_Concept
(	O
WWAN	B-General_Concept
)	O
,	O
and	O
solid-state	B-Device
drives	I-Device
(	O
SSDs	B-Device
)	O
.	O
</s>
<s>
The	O
SATA	O
revision	O
3.2	O
specification	O
,	O
in	O
its	O
gold	O
revision	O
,	O
standardizes	O
M.2	B-Protocol
as	O
a	B-General_Concept
new	O
format	O
for	O
storage	O
devices	O
and	O
specifies	O
its	O
hardware	O
layout	O
.	O
</s>
<s>
Buses	B-General_Concept
exposed	O
through	O
the	O
M.2	B-Protocol
connector	O
include	O
PCI	O
Express3.0	O
and	O
newer	O
,	O
Serial	O
ATA	O
(	O
SATA	O
)	O
3.0	O
and	O
USB3.0	O
;	O
all	O
these	O
standards	O
are	O
backward	B-General_Concept
compatible	I-General_Concept
.	O
</s>
<s>
The	O
M.2	B-Protocol
specification	O
provides	O
up	O
to	O
four	O
PCI	O
Express	O
lanes	O
and	O
one	O
logical	O
SATA	O
3.0	O
(	O
6Gbit/s	O
)	O
port	O
,	O
and	O
exposes	O
them	O
through	O
the	O
same	O
connector	O
so	O
both	O
PCI	O
Express	O
and	O
SATA	O
storage	O
devices	O
may	O
exist	O
in	O
the	O
form	O
of	O
M.2	B-Protocol
modules	O
.	O
</s>
<s>
Exposed	O
PCI	O
Express	O
lanes	O
provide	O
a	B-General_Concept
pure	O
PCI	O
Express	O
connection	O
between	O
the	O
host	O
and	O
storage	O
device	O
,	O
with	O
no	O
additional	O
layers	O
of	O
bus	B-General_Concept
abstraction	O
.	O
</s>
<s>
PCI-SIG	B-Protocol
M.2	I-Protocol
specification	O
,	O
in	O
its	O
revision	O
1.0	O
,	O
provides	O
detailed	O
M.2	B-Protocol
specifications	O
.	O
</s>
<s>
Three	O
options	O
are	O
available	O
for	O
the	O
logical	O
device	O
interfaces	B-Application
and	O
command	O
sets	O
used	O
for	O
interfacing	B-Application
with	O
M.2	B-Protocol
storage	O
devices	O
,	O
which	O
may	O
be	O
used	O
depending	O
on	O
the	O
type	O
of	O
M.2	B-Protocol
storage	O
device	O
and	O
available	O
operating	B-General_Concept
system	I-General_Concept
support	O
:	O
</s>
<s>
Legacy	B-Device
SATA	O
Used	O
for	O
SATA	O
SSDs	B-Device
,	O
and	O
interfaced	O
through	O
the	O
AHCI	O
driver	O
and	O
legacy	B-Device
SATA3.0	O
(	O
6Gbit/s	O
)	O
port	O
exposed	O
through	O
the	O
M.2	B-Protocol
connector	O
.	O
</s>
<s>
PCI	O
Express	O
using	O
AHCI	O
Used	O
for	O
PCI	O
Express	O
SSDs	B-Device
and	O
interfaced	O
through	O
the	O
AHCI	O
driver	O
and	O
provided	O
PCI	O
Express	O
lanes	O
,	O
providing	O
backward	B-General_Concept
compatibility	I-General_Concept
with	O
widespread	O
SATA	O
support	O
in	O
operating	B-General_Concept
systems	I-General_Concept
at	O
the	O
cost	O
of	O
lower	O
performance	O
.	O
</s>
<s>
AHCI	O
was	O
developed	O
when	O
the	O
purpose	O
of	O
a	B-General_Concept
host	B-Architecture
bus	I-Architecture
adapter	I-Architecture
(	O
HBA	O
)	O
in	O
a	B-General_Concept
system	O
was	O
to	O
connect	O
the	O
CPU/memory	O
subsystem	O
with	O
a	B-General_Concept
much	O
slower	O
storage	O
subsystem	O
based	O
on	O
rotating	O
magnetic	B-Architecture
media	I-Architecture
;	O
as	O
a	B-General_Concept
result	O
,	O
AHCI	O
has	O
some	O
inherent	O
inefficiencies	O
when	O
applied	O
to	O
SSD	B-Device
devices	O
,	O
which	O
behave	O
much	O
more	O
like	O
RAM	B-Architecture
than	O
like	O
spinning	O
media	O
.	O
</s>
<s>
PCI	O
Express	O
using	O
NVMe	B-Application
Used	O
for	O
PCI	O
Express	O
SSDs	B-Device
and	O
interfaced	O
through	O
the	O
NVMe	B-Application
driver	O
and	O
provided	O
PCI	O
Express	O
lanes	O
,	O
as	O
a	B-General_Concept
high-performance	O
and	O
scalable	O
host	B-Application
controller	I-Application
interface	I-Application
designed	O
and	O
optimized	O
especially	O
for	O
interfacing	B-Application
with	O
PCI	O
Express	O
SSDs	B-Device
.	O
</s>
<s>
NVMe	B-Application
has	O
been	O
designed	O
from	O
the	O
ground	O
up	O
,	O
capitalizing	O
on	O
the	O
low	O
latency	O
and	O
enhanced	O
parallelism	B-Operating_System
of	O
PCI	O
Express	O
SSDs	B-Device
,	O
and	O
complementing	O
the	O
parallelism	B-Operating_System
of	O
contemporary	O
CPUs	B-General_Concept
,	O
platforms	O
and	O
applications	O
.	O
</s>
<s>
At	O
a	B-General_Concept
high	O
level	O
,	O
primary	O
advantages	O
of	O
NVMe	B-Application
over	O
AHCI	O
relate	O
to	O
NVMe	B-Application
's	O
ability	O
to	O
exploit	O
parallelism	B-Operating_System
in	O
host	O
hardware	O
and	O
software	O
,	O
based	O
on	O
its	O
design	O
advantages	O
that	O
include	O
data	O
transfers	O
with	O
fewer	O
stages	O
,	O
greater	O
depth	O
of	O
command	B-General_Concept
queues	I-General_Concept
,	O
and	O
more	O
efficient	O
interrupt	B-Application
processing	O
.	O
</s>
<s>
The	O
M.2	B-Protocol
standard	O
is	O
based	O
on	O
the	O
mSATA	O
standard	O
,	O
which	O
uses	O
the	O
existing	O
PCI	O
Express	O
Mini	O
Card	O
(	O
Mini	O
PCIe	O
)	O
form	O
factor	O
and	O
connector	O
.	O
</s>
<s>
M.2	B-Protocol
adds	O
the	O
possibility	O
of	O
larger	O
printed	O
circuit	O
boards	O
(	O
PCBs	O
)	O
,	O
allowing	O
longer	O
modules	O
and	O
double-sided	O
component	O
population	O
.	O
</s>
<s>
Consequently	O
,	O
M.2	B-Protocol
SSD	I-Protocol
modules	O
can	O
provide	O
double	O
the	O
storage	O
capacity	O
within	O
the	O
footprint	O
of	O
an	O
mSATA	O
device	O
.	O
</s>
<s>
M.2	B-Protocol
modules	O
are	O
rectangular	O
,	O
with	O
an	O
edge	O
connector	O
on	O
one	O
side	O
and	O
a	B-General_Concept
semicircular	O
mounting	O
hole	O
at	O
the	O
center	O
of	O
the	O
opposite	O
edge	O
.	O
</s>
<s>
The	O
edge	O
connector	O
has	O
75	O
positions	O
with	O
up	O
to	O
67	O
pins	O
,	O
employing	O
a	B-General_Concept
0.5mm	O
pitch	O
and	O
offsetting	O
the	O
pins	O
on	O
opposing	O
sides	O
of	O
the	O
PCB	O
from	O
each	O
other	O
.	O
</s>
<s>
The	O
M.2	B-Protocol
standard	O
allows	O
module	O
widths	O
of	O
12	O
,	O
16	O
,	O
22	O
and	O
30mm	O
,	O
and	O
lengths	O
of	O
16	O
,	O
26	O
,	O
30	O
,	O
38	O
,	O
42	O
,	O
60	O
,	O
80	O
and	O
110mm	O
.	O
</s>
<s>
Initial	O
line-up	O
of	O
the	O
commercially	O
available	O
M.2	B-Protocol
expansion	B-Device
cards	I-Device
is	O
22mm	O
wide	O
,	O
with	O
varying	O
lengths	O
of	O
30	O
,	O
42	O
,	O
60	O
,	O
80	O
and	O
110mm	O
.	O
</s>
<s>
The	O
codes	O
for	O
the	O
M.2	B-Protocol
module	O
sizes	O
contain	O
both	O
the	O
width	O
and	O
length	O
of	O
a	B-General_Concept
particular	O
module	O
;	O
for	O
example	O
,	O
"	O
2242	O
"	O
as	O
a	B-General_Concept
module	O
code	O
means	O
that	O
the	O
module	O
is	O
22mm	O
wide	O
and	O
42mm	O
long	O
,	O
while	O
"	O
2280	O
"	O
denotes	O
a	B-General_Concept
module	O
22mm	O
wide	O
and	O
80mm	O
long	O
.	O
</s>
<s>
An	O
M.2	B-Protocol
module	O
is	O
installed	O
into	O
a	B-General_Concept
mating	O
connector	O
provided	O
by	O
the	O
host	O
's	O
circuit	O
board	O
,	O
and	O
a	B-General_Concept
single	O
mounting	O
screw	O
secures	O
the	O
module	O
into	O
place	O
.	O
</s>
<s>
Different	O
host-side	O
connectors	O
are	O
used	O
for	O
single	O
-	O
and	O
double-sided	O
M.2	B-Protocol
modules	O
,	O
providing	O
different	O
amounts	O
of	O
space	O
between	O
the	O
M.2	B-Protocol
expansion	B-Device
card	I-Device
and	O
the	O
host	O
's	O
PCB	O
.	O
</s>
<s>
Circuit	O
boards	O
on	O
the	O
hosts	O
are	O
usually	O
designed	O
to	O
accept	O
multiple	O
lengths	O
of	O
M.2	B-Protocol
modules	O
,	O
which	O
means	O
that	O
the	O
sockets	O
capable	O
of	O
accepting	O
longer	O
M.2	B-Protocol
modules	O
usually	O
also	O
accept	O
shorter	O
ones	O
by	O
providing	O
different	O
positions	O
for	O
the	O
mounting	O
screw	O
.	O
</s>
<s>
The	O
PCB	O
of	O
an	O
M.2	B-Protocol
module	O
provides	O
a	B-General_Concept
75-position	O
edge	O
connector	O
;	O
depending	O
on	O
the	O
type	O
of	O
module	O
,	O
certain	O
pin	O
positions	O
are	O
removed	O
to	O
present	O
one	O
or	O
more	O
keying	O
notches	O
.	O
</s>
<s>
Host-side	O
M.2	B-Protocol
connectors	O
(	O
sockets	O
)	O
may	O
populate	O
one	O
or	O
more	O
mating	O
key	O
positions	O
,	O
determining	O
the	O
type	O
of	O
modules	O
accepted	O
by	O
the	O
host	O
;	O
,	O
host-side	O
connectors	O
are	O
available	O
with	O
only	O
one	O
mating	O
key	O
position	O
populated	O
(	O
either	O
B	O
or	O
M	O
)	O
.	O
</s>
<s>
Furthermore	O
,	O
M.2	B-Protocol
sockets	O
keyed	O
for	O
SATA	O
or	O
two	O
PCI	O
Express	O
lanes	O
(	O
PCIe×2	O
)	O
are	O
referred	O
to	O
as	O
"	O
socket2	O
configuration	O
"	O
or	O
"	O
socket2	O
"	O
,	O
while	O
the	O
sockets	O
keyed	O
for	O
four	O
PCI	O
Express	O
lanes	O
(	O
PCIe×4	O
)	O
are	O
referred	O
to	O
as	O
"	O
socket3	O
configuration	O
"	O
or	O
"	O
socket3	O
"	O
.	O
</s>
<s>
For	O
example	O
,	O
M.2	B-Protocol
modules	O
with	O
two	O
notches	O
in	O
B	O
and	O
M	O
positions	O
use	O
up	O
to	O
two	O
PCI	O
Express	O
lanes	O
and	O
provide	O
broader	O
compatibility	O
at	O
the	O
same	O
time	O
,	O
while	O
the	O
M.2	B-Protocol
modules	O
with	O
only	O
one	O
notch	O
in	O
the	O
M	O
position	O
use	O
up	O
to	O
four	O
PCI	O
Express	O
lanes	O
;	O
both	O
examples	O
may	O
also	O
provide	O
SATA	O
storage	O
devices	O
.	O
</s>
<s>
Similar	O
keying	O
applies	O
to	O
M.2	B-Protocol
modules	O
that	O
utilize	O
provided	O
USB3.0	O
connectivity	O
.	O
</s>
<s>
Various	O
types	O
of	O
M.2	B-Protocol
modules	O
are	O
denoted	O
using	O
the	O
"	O
WWLL-HH-K-K	O
"	O
or	O
"	O
WWLL-HH-K	O
"	O
naming	O
schemes	O
,	O
in	O
which	O
"	O
WW	O
"	O
and	O
"	O
LL	O
"	O
specify	O
the	O
module	O
width	O
and	O
length	O
in	O
millimeters	O
,	O
respectively	O
.	O
</s>
<s>
The	O
"	O
HH	O
"	O
part	O
specifies	O
,	O
in	O
an	O
encoded	O
form	O
,	O
whether	O
a	B-General_Concept
module	O
is	O
single	O
-	O
or	O
double-sided	O
,	O
and	O
the	O
maximum	O
allowed	O
thickness	O
of	O
mounted	O
components	O
;	O
possible	O
values	O
are	O
listed	O
in	O
the	O
right	O
table	O
above	O
.	O
</s>
<s>
Module	O
keying	O
is	O
specified	O
by	O
the	O
"	O
K-K	O
"	O
part	O
,	O
in	O
an	O
encoded	O
form	O
using	O
the	O
key	O
IDs	O
from	O
the	O
left	O
table	O
above	O
;	O
it	O
can	O
also	O
be	O
specified	O
as	O
"	O
K	O
"	O
only	O
,	O
if	O
a	B-General_Concept
module	O
has	O
only	O
one	O
keying	O
notch	O
.	O
</s>
<s>
Beside	O
socketed	O
modules	O
,	O
the	O
M.2	B-Protocol
standard	O
also	O
includes	O
the	O
option	O
for	O
having	O
permanently	O
soldered	O
single-sided	O
modules	O
.	O
</s>
<s>
Samsung	B-Application
introduced	O
a	B-General_Concept
new	O
form	O
factor	O
called	O
Next	O
Generation	O
Small	O
Form	O
Factor	O
(	O
NGSFF	O
)	O
,	O
also	O
known	O
as	O
NF1	O
or	O
M.3	O
,	O
which	O
may	O
replace	O
U.2	B-Protocol
in	O
server	O
applications	O
.	O
</s>
<s>
It	O
targets	O
to	O
replace	O
the	O
M.2	B-Protocol
form	O
factor	O
with	O
a	B-General_Concept
significantly	O
smaller	O
one	O
(	O
also	O
called	O
XT2	O
)	O
,	O
so	O
that	O
it	O
can	O
also	O
be	O
designed	O
as	O
an	O
alternative	O
to	O
soldered	O
memory	O
.	O
</s>
<s>
XFM	O
Express	O
utilizes	O
a	B-General_Concept
NVMe	B-Application
logical	O
interface	O
over	O
a	B-General_Concept
PCI	O
Express	O
physical	O
interface	O
.	O
</s>
