<s>
A	O
NVDIMM	B-Device
(	O
pronounced	O
"	O
en-vee-dimm	O
"	O
)	O
or	O
non-volatile	B-General_Concept
DIMM	B-General_Concept
is	O
a	O
type	O
of	O
persistent	O
random-access	B-Architecture
memory	I-Architecture
for	O
computers	O
using	O
widely	O
used	O
DIMM	B-General_Concept
form-factors	O
.	O
</s>
<s>
Non-volatile	B-General_Concept
memory	I-General_Concept
is	O
memory	O
that	O
retains	O
its	O
contents	O
even	O
when	O
electrical	O
power	O
is	O
removed	O
,	O
for	O
example	O
from	O
an	O
unexpected	O
power	O
loss	O
,	O
system	O
crash	O
,	O
or	O
normal	O
shutdown	O
.	O
</s>
<s>
Properly	O
used	O
,	O
NVDIMMs	B-Device
can	O
improve	O
application	O
performance	O
and	O
system	O
crash	O
recovery	O
time	O
.	O
</s>
<s>
They	O
enhance	O
solid-state	B-Device
drive	I-Device
(	O
SSD	B-Device
)	O
endurance	O
and	O
reliability	O
.	O
</s>
<s>
Many	O
"	O
non-volatile	B-General_Concept
"	O
products	O
use	O
volatile	O
memory	O
during	O
normal	O
operation	O
and	O
dump	O
the	O
contents	O
into	O
non-volatile	B-General_Concept
memory	I-General_Concept
if	O
the	O
power	O
fails	O
,	O
using	O
an	O
on-board	O
backup	O
power	O
source	O
.	O
</s>
<s>
Volatile	O
memory	O
is	O
faster	O
than	O
non-volatile	B-General_Concept
;	O
it	O
is	O
byte-addressable	O
;	O
and	O
it	O
can	O
be	O
written	O
to	O
arbitrarily	O
,	O
without	O
concerns	O
about	O
wear	O
and	O
device	O
lifespan	O
.	O
</s>
<s>
However	O
,	O
including	O
a	O
second	O
memory	O
to	O
achieve	O
non-volatility	B-General_Concept
(	O
and	O
the	O
on-board	O
backup	O
power	O
source	O
)	O
increases	O
the	O
product	O
cost	O
compared	O
to	O
volatile	O
memory	O
.	O
</s>
<s>
There	O
are	O
many	O
emerging	O
non-volatile	B-General_Concept
memories	I-General_Concept
in	O
development	O
and	O
a	O
few	O
that	O
have	O
been	O
launched	O
including	O
Magnetoresistive	B-General_Concept
RAM	I-General_Concept
(	O
MRAM	B-General_Concept
)	O
and	O
Intel	O
's	O
3D	B-Device
XPoint	I-Device
.	O
</s>
<s>
Like	O
MRAM	B-General_Concept
,	O
Nano-RAM	O
based	O
on	O
carbon	O
nanotubes	O
is	O
one	O
technology	O
intended	O
to	O
come	O
close	O
to	O
DRAM	O
on	O
the	O
criteria	O
of	O
performance	O
,	O
byte-addressability	O
and	O
device	O
lifespan	O
;	O
first	O
products	O
are	O
expected	O
in	O
2021	O
at	O
moderate	O
density	O
,	O
from	O
fabrication	O
partner	O
Fujitsu	O
.	O
</s>
<s>
The	O
goal	O
of	O
this	O
technology	O
is	O
able	O
to	O
scale	O
cost-effectively	O
scale	O
out	O
so	O
persistent	B-Library
memory	I-Library
could	O
replace	O
DRAM	O
as	O
the	O
main	O
system	O
memory	O
in	O
enterprise	O
systems	O
.	O
</s>
<s>
There	O
are	O
three	O
types	O
of	O
NVDIMM	B-Device
implementations	O
by	O
JEDEC	O
Standards	O
org	O
:	O
</s>
<s>
NVDIMM-F	O
:	O
DIMM	B-General_Concept
with	O
flash	B-Device
storage	I-Device
.	O
</s>
<s>
System	O
users	O
will	O
need	O
to	O
pair	O
the	O
storage	O
DIMM	B-General_Concept
alongside	O
a	O
traditional	O
DRAM	O
DIMM	B-General_Concept
.	O
</s>
<s>
While	O
there	O
's	O
no	O
official	O
standard	O
,	O
NVDIMM-F	O
type	O
of	O
modules	O
have	O
been	O
available	O
since	O
2014	O
.	O
</s>
<s>
NVDIMM-N	O
:	O
DIMM	B-General_Concept
with	O
flash	B-Device
storage	I-Device
and	O
traditional	O
DRAM	O
on	O
the	O
same	O
module	O
.	O
</s>
<s>
In	O
the	O
event	O
of	O
a	O
power	O
failure	O
,	O
the	O
module	O
copies	O
the	O
data	O
from	O
the	O
volatile	O
traditional	O
DRAM	O
to	O
the	O
persistent	O
flash	B-Device
memory	I-Device
,	O
and	O
copies	O
it	O
back	O
when	O
power	O
is	O
restored	O
.	O
</s>
<s>
It	O
uses	O
a	O
small	O
backup	O
power	O
source	O
for	O
the	O
module	O
while	O
the	O
data	O
in	O
DRAM	O
is	O
being	O
copied	O
to	O
the	O
flash	B-Device
storage	I-Device
.	O
</s>
<s>
NVDIMM-P	O
:	O
specification	O
fully	O
released	O
by	O
JEDEC	O
in	O
February	O
2021	O
.	O
</s>
<s>
It	O
enables	O
computer	O
main	O
memory	O
to	O
be	O
persistent	O
,	O
using	O
persistent	B-Library
memory	I-Library
technology	O
and	O
can	O
share	O
the	O
DDR4	O
or	O
DDR5	O
DIMM	B-General_Concept
interconnect	O
with	O
DRAM	O
DIMMs	B-General_Concept
.	O
</s>
<s>
Non-Standard	O
NVDIMM	B-Device
implementations	O
:	O
</s>
<s>
NVDIMM-X	O
:	O
DDR4	O
DIMM	B-General_Concept
with	O
NAND	B-Device
Flash	I-Device
storage	O
and	O
volatile	O
DRAM	O
on	O
the	O
same	O
module	O
,	O
developed	O
by	O
Xitore	O
.	O
</s>
<s>
As	O
of	O
November	O
2012	O
,	O
most	O
NVDIMMs	B-Device
used	O
NAND	B-Device
flash	I-Device
as	O
the	O
non-volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Emerging	O
memory	O
technologies	O
aim	O
to	O
achieve	O
NVDIMM	B-Device
without	O
a	O
cache	O
or	O
two	O
separate	O
memories	O
.	O
</s>
<s>
Intel	O
and	O
Micron	O
have	O
announced	O
use	O
of	O
the	O
3D	B-Device
XPoint	I-Device
PCM	B-Device
technology	O
in	O
NVDIMM-F	O
.	O
Sony	O
and	O
Viking	O
Technology	O
have	O
announced	O
an	O
NVDIMM-N	O
product	O
based	O
on	O
the	O
ReRAM	B-General_Concept
technology	O
.	O
</s>
<s>
In	O
2015	O
,	O
Samsung	B-Application
and	O
Netlist	O
announced	O
a	O
NVDIMM-P	O
product	O
,	O
possibly	O
based	O
on	O
Z-NAND	O
.	O
</s>
<s>
NVDIMMs	B-Device
evolved	O
from	O
the	O
BBU	O
(	O
battery	O
backed	O
up	O
)	O
DIMM	B-General_Concept
,	O
which	O
used	O
a	O
backup	B-Algorithm
battery	I-Algorithm
to	O
sustain	O
power	O
to	O
a	O
volatile	O
memory	O
for	O
up	O
to	O
72	O
hours	O
.	O
</s>
<s>
When	O
the	O
module	O
includes	O
non-volatile	B-General_Concept
memory	I-General_Concept
,	O
backup	O
power	O
is	O
required	O
for	O
only	O
a	O
short	O
time	O
after	O
the	O
computer	O
's	O
main	O
power	O
fails	O
,	O
while	O
the	O
module	O
copies	O
the	O
data	O
from	O
volatile	O
to	O
non-volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Therefore	O
,	O
modern	O
NVDIMMs	B-Device
use	O
on-board	O
supercapacitors	O
to	O
store	O
energy	O
.	O
</s>
<s>
A	O
few	O
server	O
vendors	O
still	O
make	O
products	O
using	O
the	O
DDR3	O
interface	O
to	O
the	O
computer	O
,	O
but	O
standardization	O
work	O
in	O
2014	O
and	O
2015	O
,	O
such	O
as	O
at	O
JEDEC	O
and	O
ACPI	B-Device
,	O
was	O
based	O
on	O
the	O
DDR4	O
interface	O
.	O
</s>
<s>
The	O
BBU	O
DIMM	B-General_Concept
was	O
originally	O
designed	O
for	O
use	O
as	O
the	O
cache	O
of	O
RAID	B-Architecture
HBAs	O
(	O
host	O
bus	O
adapters	O
)	O
or	O
systems	O
,	O
to	O
enable	O
data	O
in	O
the	O
cache	O
to	O
survive	O
a	O
power	O
failure	O
.	O
</s>
<s>
NVDIMMs	B-Device
have	O
moved	O
beyond	O
RAID	B-Architecture
applications	O
into	O
fast	O
storage	O
appliances	O
or	O
in-memory	O
processing	O
for	O
the	O
data	B-Operating_System
center	I-Operating_System
and	O
cloud	B-Architecture
computing	I-Architecture
.	O
</s>
