<s>
Parallel	B-Protocol
ATA	I-Protocol
(	O
PATA	B-Protocol
)	O
,	O
originally	O
,	O
also	O
known	O
as	O
IDE	B-Protocol
,	O
is	O
a	O
standard	O
interface	O
designed	O
for	O
IBM	O
PC-compatible	O
computers	O
.	O
</s>
<s>
It	O
was	O
first	O
developed	O
by	O
Western	O
Digital	O
and	O
Compaq	O
in	O
1986	O
for	O
compatible	O
hard	B-Device
drives	I-Device
and	O
CD	O
or	O
DVD	O
drives	O
.	O
</s>
<s>
The	O
connection	O
is	O
used	O
for	O
storage	B-General_Concept
devices	O
such	O
as	O
hard	B-Device
disk	I-Device
drives	I-Device
,	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
and	O
optical	O
disc	O
drives	O
in	O
computers	O
.	O
</s>
<s>
The	O
Parallel	B-Protocol
ATA	I-Protocol
standard	O
is	O
the	O
result	O
of	O
a	O
long	O
history	O
of	O
incremental	O
technical	O
development	O
,	O
which	O
began	O
with	O
the	O
original	O
AT	B-Protocol
Attachment	I-Protocol
interface	I-Protocol
,	O
developed	O
for	O
use	O
in	O
early	O
PC	B-Operating_System
AT	I-Operating_System
equipment	O
.	O
</s>
<s>
The	O
ATA	O
interface	O
itself	O
evolved	O
in	O
several	O
stages	O
from	O
Western	O
Digital	O
's	O
original	O
Integrated	B-Protocol
Drive	I-Protocol
Electronics	I-Protocol
(	O
IDE	B-Protocol
)	O
interface	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
many	O
near-synonyms	O
for	O
ATA/ATAPI	B-Protocol
and	O
its	O
previous	O
incarnations	O
are	O
still	O
in	O
common	O
informal	O
use	O
,	O
in	O
particular	O
Extended	O
IDE	B-Protocol
(	O
EIDE	O
)	O
and	O
Ultra	B-Protocol
ATA	I-Protocol
(	O
UATA	B-Protocol
)	O
.	O
</s>
<s>
After	O
the	O
introduction	O
of	O
SATA	O
in	O
2003	O
,	O
the	O
original	O
ATA	O
was	O
renamed	O
to	O
Parallel	B-Protocol
ATA	I-Protocol
,	O
or	O
PATA	B-Protocol
for	O
short	O
.	O
</s>
<s>
Parallel	B-Protocol
ATA	I-Protocol
cables	O
have	O
a	O
maximum	O
allowable	O
length	O
of	O
.	O
</s>
<s>
Because	O
of	O
this	O
limit	O
,	O
the	O
technology	O
normally	O
appears	O
as	O
an	O
internal	O
computer	B-General_Concept
storage	I-General_Concept
interface	O
.	O
</s>
<s>
The	O
standard	O
was	O
originally	O
conceived	O
as	O
the	O
"	O
AT	B-Architecture
Bus	I-Architecture
Attachment	O
,	O
"	O
officially	O
called	O
"	O
AT	B-Protocol
Attachment	I-Protocol
"	O
and	O
abbreviated	O
"	O
ATA	O
"	O
because	O
its	O
primary	O
feature	O
was	O
a	O
direct	O
connection	O
to	O
the	O
16-bit	O
ISA	B-Architecture
bus	I-Architecture
introduced	O
with	O
the	O
IBM	B-Operating_System
PC/AT	I-Operating_System
.	O
</s>
<s>
The	O
original	O
ATA	O
specifications	O
published	O
by	O
the	O
standards	O
committees	O
use	O
the	O
name	O
"	O
AT	B-Protocol
Attachment	I-Protocol
"	O
.	O
</s>
<s>
The	O
"	O
AT	O
"	O
in	O
the	O
IBM	B-Operating_System
PC/AT	I-Operating_System
referred	O
to	O
"	O
Advanced	O
Technology	O
"	O
so	O
ATA	O
has	O
also	O
been	O
referred	O
to	O
as	O
"	O
Advanced	B-Protocol
Technology	I-Protocol
Attachment	I-Protocol
"	O
.	O
</s>
<s>
When	O
a	O
newer	O
Serial	O
ATA	O
(	O
SATA	O
)	O
was	O
introduced	O
in	O
2003	O
,	O
the	O
original	O
ATA	O
was	O
renamed	O
to	O
Parallel	B-Protocol
ATA	I-Protocol
,	O
or	O
PATA	B-Protocol
for	O
short	O
.	O
</s>
<s>
Physical	O
ATA	O
interfaces	O
became	O
a	O
standard	O
component	O
in	O
all	O
PCs	B-Device
,	O
initially	O
on	O
host	B-Architecture
bus	I-Architecture
adapters	I-Architecture
,	O
sometimes	O
on	O
a	O
sound	O
card	O
but	O
ultimately	O
as	O
two	O
physical	O
interfaces	O
embedded	O
in	O
a	O
Southbridge	B-Device
chip	O
on	O
a	O
motherboard	B-Device
.	O
</s>
<s>
Called	O
the	O
"	O
primary	O
"	O
and	O
"	O
secondary	O
"	O
ATA	O
interfaces	O
,	O
they	O
were	O
assigned	O
to	O
base	B-Device
addresses	I-Device
0x1F0	O
and	O
0x170	O
on	O
ISA	B-Architecture
bus	I-Architecture
systems	O
.	O
</s>
<s>
The	O
first	O
version	O
of	O
what	O
is	O
now	O
called	O
the	O
ATA/ATAPI	B-Protocol
interface	O
was	O
developed	O
by	O
Western	O
Digital	O
under	O
the	O
name	O
Integrated	B-Protocol
Drive	I-Protocol
Electronics	I-Protocol
(	O
IDE	B-Protocol
)	O
.	O
</s>
<s>
Together	O
with	O
Control	O
Data	O
Corporation	O
(	O
the	O
hard	B-Device
drive	I-Device
manufacturer	O
)	O
and	O
Compaq	O
Computer	O
(	O
the	O
initial	O
customer	O
)	O
,	O
they	O
developed	O
the	O
connector	O
,	O
the	O
signaling	O
protocols	O
and	O
so	O
on	O
,	O
with	O
the	O
goal	O
of	O
remaining	O
software	O
compatible	O
with	O
the	O
existing	O
ST-506	B-Device
hard	B-Device
drive	I-Device
interface	O
.	O
</s>
<s>
The	O
first	O
such	O
drives	O
appeared	O
internally	O
in	O
Compaq	O
PCs	B-Device
in	O
1986	O
and	O
were	O
first	O
separately	O
offered	O
by	O
Conner	O
Peripherals	O
as	O
the	O
CP342	O
in	O
June	O
1987	O
.	O
</s>
<s>
The	O
term	O
Integrated	B-Protocol
Drive	I-Protocol
Electronics	I-Protocol
refers	O
to	O
the	O
fact	O
that	O
the	O
drive	B-General_Concept
controller	I-General_Concept
is	O
integrated	O
into	O
the	O
drive	O
,	O
as	O
opposed	O
to	O
a	O
separate	O
controller	O
situated	O
at	O
the	O
other	O
side	O
of	O
the	O
connection	O
cable	O
to	O
the	O
drive	O
.	O
</s>
<s>
On	O
an	O
IBM	B-Device
PC	I-Device
compatible	O
,	O
CP/M	B-Application
machine	O
,	O
or	O
similar	O
,	O
this	O
was	O
typically	O
a	O
card	O
installed	O
on	O
a	O
motherboard	B-Device
.	O
</s>
<s>
The	O
interface	O
cards	O
used	O
to	O
connect	O
a	O
parallel	B-Protocol
ATA	I-Protocol
drive	O
to	O
,	O
for	O
example	O
,	O
an	O
ISA	B-Architecture
Slot	I-Architecture
,	O
are	O
not	O
drive	B-General_Concept
controllers	I-General_Concept
:	O
they	O
are	O
merely	O
bridges	B-Architecture
between	I-Architecture
the	I-Architecture
host	I-Architecture
bus	I-Architecture
and	I-Architecture
the	I-Architecture
ATA	I-Architecture
interface	I-Architecture
.	O
</s>
<s>
Since	O
the	O
original	O
ATA	O
interface	O
is	O
essentially	O
just	O
a	O
16-bit	O
ISA	B-Architecture
bus	I-Architecture
in	O
disguise	O
,	O
the	O
bridge	O
was	O
especially	O
simple	O
in	O
case	O
of	O
an	O
ATA	O
connector	O
being	O
located	O
on	O
an	O
ISA	O
interface	O
card	O
.	O
</s>
<s>
This	O
relieved	O
the	O
mainboard	B-Device
and	O
interface	O
cards	O
in	O
the	O
host	O
computer	O
of	O
the	O
chores	O
of	O
stepping	O
the	O
disk	O
head	O
arm	O
,	O
moving	O
the	O
head	O
arm	O
in	O
and	O
out	O
,	O
and	O
so	O
on	O
,	O
as	O
had	O
to	O
be	O
done	O
with	O
earlier	O
ST-506	B-Device
and	O
ESDI	B-Architecture
hard	B-Device
drives	I-Device
.	O
</s>
<s>
The	O
interface	O
used	O
by	O
these	O
drives	O
was	O
standardized	O
in	O
1994	O
as	O
ANSI	O
standard	O
X3.221-1994	O
,	O
AT	B-Protocol
Attachment	I-Protocol
Interface	I-Protocol
for	O
Disk	O
Drives	O
.	O
</s>
<s>
A	O
short-lived	O
,	O
seldom-used	O
implementation	O
of	O
ATA	O
was	O
created	O
for	O
the	O
IBM	B-Device
XT	I-Device
and	O
similar	O
machines	O
that	O
used	O
the	O
8-bit	O
version	O
of	O
the	O
ISA	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
It	O
has	O
been	O
referred	O
to	O
as	O
"	O
XT-IDE	O
"	O
,	O
"	O
XTA	O
"	O
or	O
"	O
XT	O
Attachment	O
"	O
.	O
</s>
<s>
In	O
1994	O
,	O
about	O
the	O
same	O
time	O
that	O
the	O
ATA-1	O
standard	O
was	O
adopted	O
,	O
Western	O
Digital	O
introduced	O
drives	O
under	O
a	O
newer	O
name	O
,	O
Enhanced	B-Protocol
IDE	I-Protocol
(	O
EIDE	O
)	O
.	O
</s>
<s>
These	O
included	O
most	O
of	O
the	O
features	O
of	O
the	O
forthcoming	O
ATA-2	B-Protocol
specification	O
and	O
several	O
additional	O
enhancements	O
.	O
</s>
<s>
Other	O
manufacturers	O
introduced	O
their	O
own	O
variations	O
of	O
ATA-1	O
such	O
as	O
"	O
Fast	B-Protocol
ATA	I-Protocol
"	O
and	O
"	O
Fast	O
ATA-2	O
"	O
.	O
</s>
<s>
The	O
new	O
version	O
of	O
the	O
ANSI	O
standard	O
,	O
AT	B-Protocol
Attachment	I-Protocol
Interface	I-Protocol
with	O
Extensions	O
ATA-2	B-Protocol
(	O
X3.279-1996	O
)	O
,	O
was	O
approved	O
in	O
1996	O
.	O
</s>
<s>
ATA-2	B-Protocol
also	O
was	O
the	O
first	O
to	O
note	O
that	O
devices	O
other	O
than	O
hard	B-Device
drives	I-Device
could	O
be	O
attached	O
to	O
the	O
interface	O
:	O
</s>
<s>
As	O
mentioned	O
in	O
the	O
previous	O
sections	O
,	O
ATA	O
was	O
originally	O
designed	O
for	O
,	O
and	O
worked	O
only	O
with	O
hard	B-Device
disk	I-Device
drives	I-Device
and	O
devices	O
that	O
could	O
emulate	O
them	O
.	O
</s>
<s>
The	O
introduction	O
of	O
ATAPI	O
(	O
ATA	O
Packet	O
Interface	O
)	O
by	O
a	O
group	O
called	O
the	O
Small	O
Form	O
Factor	O
committee	O
(	O
SFF	O
)	O
allowed	O
ATA	O
to	O
be	O
used	O
for	O
a	O
variety	O
of	O
other	O
devices	O
that	O
require	O
functions	O
beyond	O
those	O
necessary	O
for	O
hard	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
ATAPI	O
is	O
actually	O
a	O
protocol	O
allowing	O
the	O
ATA	O
interface	O
to	O
carry	O
SCSI	B-Architecture
commands	O
and	O
responses	O
;	O
therefore	O
,	O
all	O
ATAPI	O
devices	O
are	O
actually	O
"	O
speaking	O
SCSI	B-Architecture
"	O
other	O
than	O
at	O
the	O
electrical	O
interface	O
.	O
</s>
<s>
In	O
fact	O
,	O
some	O
early	O
ATAPI	O
devices	O
were	O
simply	O
SCSI	B-Architecture
devices	O
with	O
an	O
ATA/ATAPI	B-Protocol
to	O
SCSI	B-Architecture
protocol	O
converter	O
added	O
on	O
.	O
</s>
<s>
The	O
SCSI	B-Architecture
commands	O
and	O
responses	O
are	O
embedded	O
in	O
"	O
packets	O
"	O
(	O
hence	O
"	O
ATA	O
Packet	O
Interface	O
"	O
)	O
for	O
transmission	O
on	O
the	O
ATA	O
cable	O
.	O
</s>
<s>
This	O
allows	O
any	O
device	O
class	O
for	O
which	O
a	O
SCSI	B-Architecture
command	O
set	O
has	O
been	O
defined	O
to	O
be	O
interfaced	O
via	O
ATA/ATAPI	B-Protocol
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
ATA	O
hard	B-Device
drives	I-Device
and	O
solid	B-Device
state	I-Device
drives	I-Device
do	O
not	O
use	O
ATAPI	O
.	O
</s>
<s>
ATAPI	O
devices	O
include	O
CD-ROM	B-Device
and	O
DVD-ROM	O
drives	O
,	O
tape	O
drives	O
,	O
and	O
large-capacity	O
floppy	B-Device
drives	I-Device
such	O
as	O
the	O
Zip	B-Operating_System
drive	I-Operating_System
and	O
SuperDisk	B-Device
drive	I-Device
.	O
</s>
<s>
The	O
SCSI	B-Architecture
commands	O
and	O
responses	O
used	O
by	O
each	O
class	O
of	O
ATAPI	O
device	O
(	O
CD-ROM	B-Device
,	O
tape	O
,	O
etc	O
.	O
)	O
</s>
<s>
are	O
described	O
in	O
other	O
documents	O
or	O
specifications	O
specific	O
to	O
those	O
device	O
classes	O
and	O
are	O
not	O
within	O
ATA/ATAPI	B-Protocol
or	O
the	O
T13	O
committee	O
's	O
purview	O
.	O
</s>
<s>
One	O
commonly	O
used	O
set	O
is	O
defined	O
in	O
the	O
MMC	O
SCSI	B-Architecture
command	O
set	O
.	O
</s>
<s>
ATAPI	O
was	O
adopted	O
as	O
part	O
of	O
ATA	O
in	O
INCITS	O
317-1998	O
,	O
AT	B-Protocol
Attachment	I-Protocol
with	I-Protocol
Packet	I-Protocol
Interface	I-Protocol
Extension	O
(	O
ATA/ATAPI	B-Protocol
-4	O
)	O
.	O
</s>
<s>
The	O
ATA/ATAPI	B-Protocol
-4	O
standard	O
also	O
introduced	O
several	O
"	O
Ultra	O
DMA	O
"	O
transfer	O
modes	O
.	O
</s>
<s>
The	O
latest	O
versions	O
of	O
Parallel	B-Protocol
ATA	I-Protocol
support	O
up	O
to	O
133	O
MByte/s	O
.	O
</s>
<s>
Ultra	B-Protocol
ATA	I-Protocol
,	O
abbreviated	O
UATA	B-Protocol
,	O
is	O
a	O
designation	O
that	O
has	O
been	O
primarily	O
used	O
by	O
Western	O
Digital	O
for	O
different	O
speed	O
enhancements	O
to	O
the	O
ATA/ATAPI	B-Protocol
standards	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
2000	O
Western	O
Digital	O
published	O
a	O
document	O
describing	O
"	O
Ultra	O
ATA/100	O
"	O
,	O
which	O
brought	O
performance	O
improvements	O
for	O
the	O
then-current	O
ATA/ATAPI	B-Protocol
-5	O
standard	O
by	O
improving	O
maximum	O
speed	O
of	O
the	O
Parallel	B-Protocol
ATA	I-Protocol
interface	O
from	O
66	O
to	O
100MB/s	O
.	O
</s>
<s>
Most	O
of	O
Western	O
Digital	O
's	O
changes	O
,	O
along	O
with	O
others	O
,	O
were	O
included	O
in	O
the	O
ATA/ATAPI	B-Protocol
-6	O
standard	O
(	O
2002	O
)	O
.	O
</s>
<s>
The	O
terms	O
"	O
integrated	B-Protocol
drive	I-Protocol
electronics	I-Protocol
"	O
(	O
IDE	B-Protocol
)	O
,	O
"	O
enhanced	B-Protocol
IDE	I-Protocol
"	O
and	O
"	O
EIDE	O
"	O
have	O
come	O
to	O
be	O
used	O
interchangeably	O
with	O
ATA	O
(	O
now	O
Parallel	B-Protocol
ATA	I-Protocol
,	O
or	O
PATA	B-Protocol
)	O
.	O
</s>
<s>
An	O
early	O
"	O
EIDE	O
"	O
drive	O
might	O
be	O
compatible	O
with	O
ATA-2	B-Protocol
,	O
while	O
a	O
later	O
one	O
with	O
ATA-6	B-Protocol
.	O
</s>
<s>
Nevertheless	O
,	O
a	O
request	O
for	O
an	O
"	O
IDE	B-Protocol
"	O
or	O
"	O
EIDE	O
"	O
drive	O
from	O
a	O
computer	O
parts	O
vendor	O
will	O
almost	O
always	O
yield	O
a	O
drive	O
that	O
will	O
work	O
with	O
most	O
Parallel	B-Protocol
ATA	I-Protocol
interfaces	O
.	O
</s>
<s>
ATA-4	O
drives	O
are	O
thus	O
sometimes	O
called	O
"	O
UDMA-33	O
"	O
drives	O
,	O
and	O
sometimes	O
"	O
ATA-33	B-Protocol
"	O
drives	O
.	O
</s>
<s>
Similarly	O
,	O
ATA-6	B-Protocol
introduced	O
a	O
maximum	O
transfer	B-Device
speed	I-Device
of	O
100	O
megabytes	O
per	O
second	O
,	O
and	O
some	O
drives	O
complying	O
with	O
this	O
version	O
of	O
the	O
standard	O
are	O
marketed	O
as	O
"	O
PATA/100	O
"	O
drives	O
.	O
</s>
<s>
Initially	O
,	O
the	O
size	O
of	O
an	O
ATA	B-Protocol
drive	I-Protocol
was	O
stored	O
in	O
the	O
system	O
x86	B-Operating_System
BIOS	B-Operating_System
using	O
a	O
type	O
number	O
(	O
1	O
through	O
45	O
)	O
that	O
predefined	O
the	O
C/H/S	B-Device
parameters	O
and	O
also	O
often	O
the	O
landing	O
zone	O
,	O
in	O
which	O
the	O
drive	O
heads	O
are	O
parked	O
while	O
not	O
in	O
use	O
.	O
</s>
<s>
Later	O
,	O
a	O
"	O
user	O
definable	O
"	O
format	O
called	O
C/H/S	B-Device
or	O
cylinders	O
,	O
heads	O
,	O
sectors	B-Application
was	O
made	O
available	O
.	O
</s>
<s>
These	O
numbers	O
were	O
important	O
for	O
the	O
earlier	O
ST-506	B-Device
interface	O
,	O
but	O
were	O
generally	O
meaningless	O
for	O
ATA	O
—	O
the	O
CHS	B-Device
parameters	O
for	O
later	O
ATA	O
large	O
drives	O
often	O
specified	O
impossibly	O
high	O
numbers	O
of	O
heads	O
or	O
sectors	B-Application
that	O
did	O
not	O
actually	O
define	O
the	O
internal	O
physical	O
layout	O
of	O
the	O
drive	O
at	O
all	O
.	O
</s>
<s>
From	O
the	O
start	O
,	O
and	O
up	O
to	O
ATA-2	B-Protocol
,	O
every	O
user	O
had	O
to	O
specify	O
explicitly	O
how	O
large	O
every	O
attached	O
drive	O
was	O
.	O
</s>
<s>
From	O
ATA-2	B-Protocol
on	O
,	O
an	O
"	O
identify	O
drive	O
"	O
command	O
was	O
implemented	O
that	O
can	O
be	O
sent	O
and	O
which	O
will	O
return	O
all	O
drive	O
parameters	O
.	O
</s>
<s>
Owing	O
to	O
a	O
lack	O
of	O
foresight	O
by	O
motherboard	B-Device
manufacturers	O
,	O
the	O
system	B-Operating_System
BIOS	I-Operating_System
was	O
often	O
hobbled	O
by	O
artificial	O
C/H/S	B-Device
size	O
limitations	O
due	O
to	O
the	O
manufacturer	O
assuming	O
certain	O
values	O
would	O
never	O
exceed	O
a	O
particular	O
numerical	O
maximum	O
.	O
</s>
<s>
The	O
first	O
of	O
these	O
BIOS	B-Operating_System
limits	O
occurred	O
when	O
ATA	B-Protocol
drives	I-Protocol
reached	O
sizes	O
in	O
excess	O
of	O
504	O
MiB	O
,	O
because	O
some	O
motherboard	B-Device
BIOSes	O
would	O
not	O
allow	O
C/H/S	B-Device
values	O
above	O
1024	O
cylinders	O
,	O
16	O
heads	O
,	O
and	O
63	O
sectors	B-Application
.	O
</s>
<s>
Multiplied	O
by	O
512	B-Application
bytes	I-Application
per	O
sector	O
,	O
this	O
totals	O
bytes	O
which	O
,	O
divided	O
by	O
bytes	O
per	O
MiB	O
,	O
equals	O
504	O
MiB	O
(	O
528	O
MB	O
)	O
.	O
</s>
<s>
The	O
second	O
of	O
these	O
BIOS	B-Operating_System
limitations	O
occurred	O
at	O
1024	O
cylinders	O
,	O
256	O
heads	O
,	O
and	O
63	O
sectors	B-Application
,	O
and	O
a	O
problem	O
in	O
MS-DOS	B-Application
limited	O
the	O
number	O
of	O
heads	O
to	O
255	O
.	O
</s>
<s>
This	O
is	O
again	O
a	O
limit	O
imposed	O
by	O
x86	B-Operating_System
BIOSes	O
,	O
and	O
not	O
a	O
limit	O
imposed	O
by	O
the	O
ATA	O
interface	O
.	O
</s>
<s>
It	O
was	O
eventually	O
determined	O
that	O
these	O
size	O
limitations	O
could	O
be	O
overridden	O
with	O
a	O
small	O
program	O
loaded	O
at	O
startup	O
from	O
a	O
hard	B-Device
drive	I-Device
's	O
boot	B-Device
sector	I-Device
.	O
</s>
<s>
Some	O
hard	B-Device
drive	I-Device
manufacturers	O
,	O
such	O
as	O
Western	O
Digital	O
,	O
started	O
including	O
these	O
override	O
utilities	O
with	O
large	O
hard	B-Device
drives	I-Device
to	O
help	O
overcome	O
these	O
problems	O
.	O
</s>
<s>
However	O
,	O
if	O
the	O
computer	O
was	O
booted	O
in	O
some	O
other	O
manner	O
without	O
loading	O
the	O
special	O
utility	O
,	O
the	O
invalid	O
BIOS	B-Operating_System
settings	I-Operating_System
would	O
be	O
used	O
and	O
the	O
drive	O
could	O
either	O
be	O
inaccessible	O
or	O
appear	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
be	O
damaged	O
.	O
</s>
<s>
Later	O
,	O
an	O
extension	O
to	O
the	O
x86	B-Operating_System
BIOS	B-Operating_System
disk	B-Device
services	I-Device
called	O
the	O
"	O
Enhanced	O
Disk	O
Drive	O
"	O
(	O
EDD	O
)	O
was	O
made	O
available	O
,	O
which	O
makes	O
it	O
possible	O
to	O
address	O
drives	O
as	O
large	O
as	O
264	O
sectors	B-Application
.	O
</s>
<s>
Later	O
,	O
the	O
first	O
formalized	O
ATA	O
specification	O
used	O
a	O
28-bit	O
addressing	O
mode	O
through	O
LBA28	O
,	O
allowing	O
for	O
the	O
addressing	O
of	O
228	O
(	O
)	O
sectors	B-Application
(	O
blocks	O
)	O
of	O
512	B-Application
bytes	I-Application
each	O
,	O
resulting	O
in	O
a	O
maximum	O
capacity	O
of	O
128	O
GiB	O
(	O
137	O
GB	O
)	O
.	O
</s>
<s>
ATA-6	B-Protocol
introduced	O
48-bit	O
addressing	O
,	O
increasing	O
the	O
limit	O
to	O
128	O
PiB	O
(	O
144	O
PB	O
)	O
.	O
</s>
<s>
As	O
a	O
consequence	O
,	O
any	O
ATA	B-Protocol
drive	I-Protocol
of	O
capacity	O
larger	O
than	O
about	O
137	O
GB	O
must	O
be	O
an	O
ATA-6	B-Protocol
or	O
later	O
drive	O
.	O
</s>
<s>
Connecting	O
such	O
a	O
drive	O
to	O
a	O
host	O
with	O
an	O
ATA-5	B-Protocol
or	O
earlier	O
interface	O
will	O
limit	O
the	O
usable	O
capacity	O
to	O
the	O
maximum	O
of	O
the	O
interface	O
.	O
</s>
<s>
Some	O
operating	B-General_Concept
systems	I-General_Concept
,	O
including	O
Windows	B-Application
XP	I-Application
pre-SP1	O
,	O
and	O
Windows	B-Application
2000	I-Application
pre-SP3	O
,	O
disable	O
LBA48	O
by	O
default	O
,	O
requiring	O
the	O
user	O
to	O
take	O
extra	O
steps	O
to	O
use	O
the	O
entire	O
capacity	O
of	O
an	O
ATA	B-Protocol
drive	I-Protocol
larger	O
than	O
about	O
137	O
gigabytes	O
.	O
</s>
<s>
Older	O
operating	B-General_Concept
systems	I-General_Concept
,	O
such	O
as	O
Windows	B-Device
98	I-Device
,	O
do	O
not	O
support	O
48-bit	O
LBA	O
at	O
all	O
.	O
</s>
<s>
However	O
,	O
members	O
of	O
the	O
third-party	O
group	O
MSFN	O
have	O
modified	O
the	O
Windows	B-Device
98	I-Device
disk	O
drivers	O
to	O
add	O
unofficial	O
support	O
for	O
48-bit	O
LBA	O
to	O
Windows	O
95	O
OSR2	O
,	O
Windows	B-Device
98	I-Device
,	O
Windows	B-Device
98	I-Device
SE	O
and	O
Windows	B-Device
ME	I-Device
.	O
</s>
<s>
Some	O
16-bit	O
and	O
32-bit	O
operating	B-General_Concept
systems	I-General_Concept
supporting	O
LBA48	O
may	O
still	O
not	O
support	O
disks	O
larger	O
than	O
2	O
TiB	O
due	O
to	O
using	O
32-bit	O
arithmetic	O
only	O
;	O
a	O
limitation	O
also	O
applying	O
to	O
many	O
boot	B-Device
sectors	I-Device
.	O
</s>
<s>
Parallel	B-Protocol
ATA	I-Protocol
(	O
then	O
simply	O
called	O
ATA	O
or	O
IDE	B-Protocol
)	O
became	O
the	O
primary	O
storage	B-General_Concept
device	O
interface	O
for	O
PCs	B-Device
soon	O
after	O
its	O
introduction	O
.	O
</s>
<s>
In	O
some	O
systems	O
,	O
a	O
third	O
and	O
fourth	O
motherboard	B-Device
interface	O
was	O
provided	O
,	O
allowing	O
up	O
to	O
eight	O
ATA	O
devices	O
to	O
be	O
attached	O
to	O
the	O
motherboard	B-Device
.	O
</s>
<s>
Often	O
,	O
these	O
additional	O
connectors	O
were	O
implemented	O
by	O
inexpensive	O
RAID	B-Architecture
controllers	O
.	O
</s>
<s>
Soon	O
after	O
the	O
introduction	O
of	O
Serial	O
ATA	O
(	O
SATA	O
)	O
in	O
2003	O
,	O
use	O
of	O
Parallel	B-Protocol
ATA	I-Protocol
declined	O
.	O
</s>
<s>
The	O
first	O
motherboards	B-Device
with	O
built-in	O
SATA	O
interfaces	O
usually	O
had	O
only	O
a	O
single	O
PATA	B-Protocol
connector	O
(	O
for	O
up	O
to	O
two	O
PATA	B-Protocol
devices	O
)	O
,	O
along	O
with	O
multiple	O
SATA	O
connectors	O
.	O
</s>
<s>
Some	O
PCs	B-Device
and	O
laptops	O
of	O
the	O
era	O
have	O
a	O
SATA	O
hard	B-Device
disk	I-Device
and	O
an	O
optical	O
drive	O
connected	O
to	O
PATA	B-Protocol
.	O
</s>
<s>
As	O
of	O
2007	O
,	O
some	O
PC	B-Device
chipsets	I-Device
,	O
for	O
example	O
the	O
Intel	O
ICH10	O
,	O
had	O
removed	O
support	O
for	O
PATA	B-Protocol
.	O
</s>
<s>
Motherboard	B-Device
vendors	O
still	O
wishing	O
to	O
offer	O
Parallel	B-Protocol
ATA	I-Protocol
with	O
those	O
chipsets	B-Device
must	O
include	O
an	O
additional	O
interface	O
chip	O
.	O
</s>
<s>
In	O
more	O
recent	O
computers	O
,	O
the	O
Parallel	B-Protocol
ATA	I-Protocol
interface	O
is	O
rarely	O
used	O
even	O
if	O
present	O
,	O
as	O
four	O
or	O
more	O
Serial	O
ATA	O
connectors	O
are	O
usually	O
provided	O
on	O
the	O
motherboard	B-Device
and	O
SATA	O
devices	O
of	O
all	O
types	O
are	O
common	O
.	O
</s>
<s>
With	O
Western	O
Digital	O
's	O
withdrawal	O
from	O
the	O
PATA	B-Protocol
market	O
,	O
hard	B-Device
disk	I-Device
drives	I-Device
with	O
the	O
PATA	B-Protocol
interface	O
were	O
no	O
longer	O
in	O
production	O
after	O
December	O
2013	O
for	O
other	O
than	O
specialty	O
applications	O
.	O
</s>
<s>
Parallel	B-Protocol
ATA	I-Protocol
cables	O
transfer	O
data	O
16	O
bits	O
at	O
a	O
time	O
.	O
</s>
<s>
Each	O
cable	O
has	O
two	O
or	O
three	O
connectors	O
,	O
one	O
of	O
which	O
plugs	O
into	O
a	O
host	B-Architecture
adapter	I-Architecture
interfacing	O
with	O
the	O
rest	O
of	O
the	O
computer	O
system	O
.	O
</s>
<s>
The	O
remaining	O
connector(s )	O
plug	O
into	O
storage	B-General_Concept
devices	O
,	O
most	O
commonly	O
hard	B-Device
disk	I-Device
drives	I-Device
or	O
optical	O
drives	O
.	O
</s>
<s>
Round	O
parallel	B-Protocol
ATA	I-Protocol
cables	O
(	O
as	O
opposed	O
to	O
ribbon	O
cables	O
)	O
were	O
eventually	O
made	O
available	O
for	O
'	O
case	B-Architecture
modders	I-Architecture
 '	O
for	O
cosmetic	O
reasons	O
,	O
as	O
well	O
as	O
claims	O
of	O
improved	O
computer	O
cooling	O
and	O
were	O
easier	O
to	O
handle	O
;	O
however	O
,	O
only	O
ribbon	O
cables	O
are	O
supported	O
by	O
the	O
ATA	O
specifications	O
.	O
</s>
<s>
However	O
,	O
some	O
flash	B-Device
memory	I-Device
drives	O
can	O
use	O
pin	O
20	O
as	O
VCC_in	O
to	O
power	O
the	O
drive	O
without	O
requiring	O
a	O
special	O
power	O
cable	O
;	O
this	O
feature	O
can	O
only	O
be	O
used	O
if	O
the	O
equipment	O
supports	O
this	O
use	O
of	O
pin	O
20	O
.	O
</s>
<s>
It	O
is	O
attached	O
normally	O
on	O
the	O
black	O
(	O
master	O
drive	O
end	O
)	O
and	O
blue	O
(	O
motherboard	B-Device
end	O
)	O
connectors	O
.	O
</s>
<s>
A	O
44-pin	O
variant	O
PATA	B-Protocol
connector	O
is	O
used	O
for	O
2.5	O
inch	O
drives	O
inside	O
laptops	O
.	O
</s>
<s>
The	O
image	O
on	O
the	O
right	O
shows	O
PATA	B-Protocol
connectors	O
after	O
removal	O
of	O
strain	O
relief	O
,	O
cover	O
,	O
and	O
cable	O
.	O
</s>
<s>
The	O
connector	O
is	O
an	O
insulation-displacement	B-Protocol
connector	I-Protocol
:	O
each	O
contact	O
comprises	O
a	O
pair	O
of	O
points	O
which	O
together	O
pierce	O
the	O
insulation	O
of	O
the	O
ribbon	O
cable	O
with	O
such	O
precision	O
that	O
they	O
make	O
a	O
connection	O
to	O
the	O
desired	O
conductor	O
without	O
harming	O
the	O
insulation	O
on	O
the	O
neighboring	O
conductors	O
.	O
</s>
<s>
Installing	O
the	O
cable	O
backwards	O
(	O
with	O
the	O
black	O
connector	O
on	O
the	O
system	B-Device
board	I-Device
,	O
the	O
blue	O
connector	O
on	O
the	O
remote	O
device	O
and	O
the	O
gray	O
connector	O
on	O
the	O
center	O
device	O
)	O
will	O
ground	O
pin	O
34	O
of	O
the	O
remote	O
device	O
and	O
connect	O
host	O
pin	O
34	O
through	O
to	O
pin	O
34	O
of	O
the	O
center	O
device	O
.	O
</s>
<s>
The	O
Device	O
0	O
drive	O
is	O
the	O
drive	O
that	O
usually	O
appears	O
"	O
first	O
"	O
to	O
the	O
computer	O
's	O
BIOS	B-Operating_System
and/or	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
In	O
most	O
personal	B-Device
computers	I-Device
the	O
drives	O
are	O
often	O
designated	O
as	O
"	O
C	O
:	O
"	O
for	O
the	O
Device	O
0	O
and	O
"	O
D	O
:	O
"	O
for	O
the	O
Device	O
1	O
referring	O
to	O
one	O
active	O
primary	O
partitions	O
on	O
each	O
.	O
</s>
<s>
The	O
mode	O
that	O
a	O
device	O
must	O
use	O
is	O
often	O
set	O
by	O
a	O
jumper	B-Device
setting	I-Device
on	O
the	O
device	O
itself	O
,	O
which	O
must	O
be	O
manually	O
set	O
to	O
Device	O
0	O
(	O
Master	O
)	O
or	O
Device	O
1	O
(	O
Slave	O
)	O
.	O
</s>
<s>
The	O
words	O
primary	O
and	O
secondary	O
typically	O
refers	O
to	O
the	O
two	O
IDE	B-Protocol
cables	I-Protocol
,	O
which	O
can	O
have	O
two	O
drives	O
each	O
(	O
primary	O
master	O
,	O
primary	O
slave	O
,	O
secondary	O
master	O
,	O
secondary	O
slave	O
)	O
.	O
</s>
<s>
A	O
drive	O
mode	O
called	O
cable	O
select	O
was	O
described	O
as	O
optional	O
in	O
ATA-1	O
and	O
has	O
come	O
into	O
fairly	O
widespread	O
use	O
with	O
ATA-5	B-Protocol
and	O
later	O
.	O
</s>
<s>
The	O
host	B-Architecture
adapter	I-Architecture
grounds	O
this	O
pin	O
;	O
if	O
a	O
device	O
sees	O
that	O
the	O
pin	O
is	O
grounded	O
,	O
it	O
becomes	O
the	O
Device	O
0	O
(	O
master	O
)	O
device	O
;	O
if	O
it	O
sees	O
that	O
pin	O
28	O
is	O
open	O
,	O
the	O
device	O
becomes	O
the	O
Device	O
1	O
(	O
slave	O
)	O
device	O
.	O
</s>
<s>
This	O
setting	O
is	O
usually	O
chosen	O
by	O
a	O
jumper	B-Device
setting	I-Device
on	O
the	O
drive	O
called	O
"	O
cable	O
select	O
"	O
,	O
usually	O
marked	O
CS	O
,	O
which	O
is	O
separate	O
from	O
the	O
Device	O
0/1	O
setting	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
the	O
manual	O
master/slave	B-Operating_System
setting	O
using	O
jumpers	B-Device
on	O
the	O
drives	O
takes	O
precedence	O
and	O
allows	O
them	O
to	O
be	O
freely	O
placed	O
on	O
either	O
connector	O
of	O
the	O
ribbon	O
cable	O
.	O
</s>
<s>
motherboard	B-Device
IDE	B-Protocol
connector	O
,	O
or	O
IDE	B-Protocol
card	O
)	O
.	O
</s>
<s>
The	O
parallel	B-Protocol
ATA	I-Protocol
protocols	O
up	O
through	O
ATA-3	B-Protocol
require	O
that	O
once	O
a	O
command	O
has	O
been	O
given	O
on	O
an	O
ATA	O
interface	O
,	O
it	O
must	O
complete	O
before	O
any	O
subsequent	O
command	O
may	O
be	O
given	O
.	O
</s>
<s>
The	O
function	O
of	O
serializing	O
requests	O
to	O
the	O
interface	O
is	O
usually	O
performed	O
by	O
a	O
device	O
driver	O
in	O
the	O
host	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
ATA-4	O
and	O
subsequent	O
versions	O
of	O
the	O
specification	O
have	O
included	O
an	O
"	O
overlapped	O
feature	O
set	O
"	O
and	O
a	O
"	O
queued	O
feature	O
set	O
"	O
as	O
optional	O
features	O
,	O
both	O
being	O
given	O
the	O
name	O
"	O
Tagged	O
Command	O
Queuing	O
"	O
(	O
TCQ	O
)	O
,	O
a	O
reference	O
to	O
a	O
set	O
of	O
features	O
from	O
SCSI	B-Architecture
which	O
the	O
ATA	O
version	O
attempts	O
to	O
emulate	O
.	O
</s>
<s>
However	O
,	O
support	O
for	O
these	O
is	O
extremely	O
rare	O
in	O
actual	O
parallel	B-Protocol
ATA	I-Protocol
products	O
and	O
device	O
drivers	O
because	O
these	O
feature	O
sets	O
were	O
implemented	O
in	O
such	O
a	O
way	O
as	O
to	O
maintain	O
software	O
compatibility	O
with	O
its	O
heritage	O
as	O
originally	O
an	O
extension	O
of	O
the	O
ISA	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
By	O
contrast	O
,	O
overlapped	O
and	O
queued	O
operations	O
have	O
been	O
common	O
in	O
other	O
storage	B-General_Concept
buses	O
;	O
in	O
particular	O
,	O
SCSI	B-Architecture
's	O
version	O
of	O
tagged	O
command	O
queuing	O
had	O
no	O
need	O
to	O
be	O
compatible	O
with	O
APIs	O
designed	O
for	O
ISA	O
,	O
allowing	O
it	O
to	O
attain	O
high	O
performance	O
with	O
low	O
overhead	O
on	O
buses	O
which	O
supported	O
first	O
party	O
DMA	O
like	O
PCI	B-Protocol
.	O
</s>
<s>
This	O
has	O
long	O
been	O
seen	O
as	O
a	O
major	O
advantage	O
of	O
SCSI	B-Architecture
.	O
</s>
<s>
The	O
Serial	O
ATA	O
standard	O
has	O
supported	O
native	O
command	O
queueing	O
(	O
NCQ	O
)	O
since	O
its	O
first	O
release	O
,	O
but	O
it	O
is	O
an	O
optional	O
feature	O
for	O
both	O
host	B-Architecture
adapters	I-Architecture
and	O
target	O
devices	O
.	O
</s>
<s>
Many	O
obsolete	O
PC	B-Device
motherboards	I-Device
do	O
not	O
support	O
NCQ	O
,	O
but	O
modern	O
SATA	O
hard	B-Device
disk	I-Device
drives	I-Device
and	O
SATA	O
solid-state	B-Device
drives	I-Device
usually	O
support	O
NCQ	O
,	O
which	O
is	O
not	O
the	O
case	O
for	O
removable	O
(	O
CD/DVD	O
)	O
drives	O
because	O
the	O
ATAPI	O
command	O
set	O
used	O
to	O
control	O
them	O
prohibits	O
queued	O
operations	O
.	O
</s>
<s>
On	O
early	O
ATA	O
host	B-Architecture
adapters	I-Architecture
,	O
both	O
devices	O
 '	O
data	O
transfers	O
can	O
be	O
constrained	O
to	O
the	O
speed	O
of	O
the	O
slower	O
device	O
,	O
if	O
two	O
devices	O
of	O
different	O
speed	O
capabilities	O
are	O
on	O
the	O
same	O
cable	O
.	O
</s>
<s>
For	O
all	O
modern	O
ATA	O
host	B-Architecture
adapters	I-Architecture
,	O
this	O
is	O
not	O
true	O
,	O
as	O
modern	O
ATA	O
host	B-Architecture
adapters	I-Architecture
support	O
independent	O
device	O
timing	O
.	O
</s>
<s>
This	O
is	O
caused	O
by	O
the	O
omission	O
of	O
both	O
overlapped	O
and	O
queued	O
feature	O
sets	O
from	O
most	O
parallel	B-Protocol
ATA	I-Protocol
products	O
.	O
</s>
<s>
However	O
,	O
most	O
modern	O
devices	O
will	O
report	O
write	O
operations	O
as	O
complete	O
once	O
the	O
data	O
is	O
stored	O
in	O
their	O
onboard	O
cache	B-Device
memory	O
,	O
before	O
the	O
data	O
is	O
written	O
to	O
the	O
(	O
slow	O
)	O
magnetic	O
storage	B-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
when	O
copying	O
data	O
from	O
an	O
optical	O
drive	O
to	O
a	O
hard	B-Device
drive	I-Device
(	O
such	O
as	O
during	O
software	O
installation	O
)	O
,	O
this	O
effect	O
probably	O
will	O
not	O
matter	O
.	O
</s>
<s>
But	O
if	O
the	O
hard	B-Device
drive	I-Device
in	O
question	O
is	O
also	O
expected	O
to	O
provide	O
good	O
throughput	O
for	O
other	O
tasks	O
at	O
the	O
same	O
time	O
,	O
it	O
probably	O
should	O
not	O
be	O
on	O
the	O
same	O
cable	O
as	O
the	O
optical	O
drive	O
.	O
</s>
<s>
There	O
is	O
an	O
attempt	O
limit	O
,	O
normally	O
set	O
to	O
5	O
,	O
after	O
which	O
the	O
disk	O
must	O
be	O
power	O
cycled	O
or	O
hard-reset	B-Operating_System
before	O
unlocking	O
can	O
be	O
attempted	O
again	O
.	O
</s>
<s>
Due	O
to	O
a	O
short	O
cable	O
length	O
specification	O
and	O
shielding	O
issues	O
it	O
is	O
extremely	O
uncommon	O
to	O
find	O
external	O
PATA	B-Protocol
devices	O
that	O
directly	O
use	O
PATA	B-Protocol
for	O
connection	O
to	O
a	O
computer	O
.	O
</s>
<s>
For	O
ease	O
of	O
reach	O
from	O
motherboard	B-Device
to	O
device	O
,	O
the	O
connectors	O
tend	O
to	O
be	O
positioned	O
towards	O
the	O
front	O
edge	O
of	O
motherboards	B-Device
,	O
for	O
connection	O
to	O
devices	O
protruding	O
from	O
the	O
front	O
of	O
the	O
computer	O
case	O
.	O
</s>
<s>
External	O
hard	B-Device
disk	I-Device
drives	I-Device
or	O
optical	O
disk	O
drives	O
that	O
have	O
an	O
internal	O
PATA	B-Protocol
interface	O
,	O
use	O
some	O
other	O
interface	O
technology	O
to	O
bridge	O
the	O
distance	O
between	O
the	O
external	O
device	O
and	O
the	O
computer	O
.	O
</s>
<s>
A	O
bridge	O
chip	O
inside	O
the	O
external	O
devices	O
converts	O
from	O
the	O
USB	O
interface	O
to	O
PATA	B-Protocol
,	O
and	O
typically	O
only	O
supports	O
a	O
single	O
external	O
device	O
without	O
cable	O
select	O
or	O
master/slave	B-Operating_System
.	O
</s>
<s>
Compact	B-Device
Flash	I-Device
in	O
its	O
IDE	B-Protocol
mode	O
is	O
essentially	O
a	O
miniaturized	O
ATA	O
interface	O
,	O
intended	O
for	O
use	O
on	O
devices	O
that	O
use	O
flash	B-Device
memory	I-Device
storage	B-General_Concept
.	O
</s>
<s>
No	O
interfacing	O
chips	O
or	O
circuitry	O
are	O
required	O
,	O
other	O
than	O
to	O
directly	O
adapt	O
the	O
smaller	O
CF	B-Device
socket	O
onto	O
the	O
larger	O
ATA	O
connector	O
.	O
</s>
<s>
The	O
ATA	O
connector	O
specification	O
does	O
not	O
include	O
pins	O
for	O
supplying	O
power	O
to	O
a	O
CF	B-Device
device	O
,	O
so	O
power	O
is	O
inserted	O
into	O
the	O
connector	O
from	O
a	O
separate	O
source	O
.	O
</s>
<s>
The	O
exception	O
to	O
this	O
is	O
when	O
the	O
CF	B-Device
device	O
is	O
connected	O
to	O
a	O
44-pin	O
ATA	O
bus	O
designed	O
for	O
2.5-inch	O
hard	B-Device
disk	I-Device
drives	I-Device
,	O
commonly	O
found	O
in	O
notebook	O
computers	O
,	O
as	O
this	O
bus	O
implementation	O
must	O
provide	O
power	O
to	O
a	O
standard	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
CF	B-Device
devices	O
can	O
be	O
designated	O
as	O
devices	O
0	O
or	O
1	O
on	O
an	O
ATA	O
interface	O
,	O
though	O
since	O
most	O
CF	B-Device
devices	O
offer	O
only	O
a	O
single	O
socket	O
,	O
it	O
is	O
not	O
necessary	O
to	O
offer	O
this	O
selection	O
to	O
end	O
users	O
.	O
</s>
<s>
Although	O
CF	B-Device
can	O
be	O
hot-pluggable	B-Device
with	O
additional	O
design	O
methods	O
,	O
by	O
default	O
when	O
wired	O
directly	O
to	O
an	O
ATA	O
interface	O
,	O
it	O
is	O
not	O
intended	O
to	O
be	O
hot-pluggable	B-Device
.	O
</s>
<s>
Note	O
that	O
the	O
transfer	O
rate	O
for	O
each	O
mode	O
(	O
for	O
example	O
,	O
66.7MB/s	O
for	O
UDMA4	O
,	O
commonly	O
called	O
"	O
Ultra-DMA	O
66	O
"	O
,	O
defined	O
by	O
ATA-5	B-Protocol
)	O
gives	O
its	O
maximum	O
theoretical	O
transfer	O
rate	O
on	O
the	O
cable	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
maximum	O
data	O
transfer	O
rate	O
for	O
conventional	B-Protocol
PCI	I-Protocol
bus	O
is	O
133MB/s	O
,	O
and	O
this	O
is	O
shared	O
among	O
all	O
active	O
devices	O
on	O
the	O
bus	O
.	O
</s>
<s>
In	O
addition	O
,	O
no	O
ATA	O
hard	B-Device
drives	I-Device
existed	O
in	O
2005	O
that	O
were	O
capable	O
of	O
measured	O
sustained	O
transfer	O
rates	O
of	O
above	O
80MB/s	O
.	O
</s>
<s>
Hard	B-Device
drive	I-Device
performance	O
under	O
most	O
workloads	O
is	O
limited	O
first	O
and	O
second	O
by	O
those	O
two	O
factors	O
;	O
the	O
transfer	O
rate	O
on	O
the	O
bus	O
is	O
a	O
distant	O
third	O
in	O
importance	O
.	O
</s>
<s>
Therefore	O
,	O
transfer	B-Device
speed	I-Device
limits	O
above	O
66MB/s	O
really	O
affect	O
performance	O
only	O
when	O
the	O
hard	B-Device
drive	I-Device
can	O
satisfy	O
all	O
I/O	O
requests	O
by	O
reading	O
from	O
its	O
internal	O
cache	B-Device
—	O
a	O
very	O
unusual	O
situation	O
,	O
especially	O
considering	O
that	O
such	O
data	O
is	O
usually	O
already	O
buffered	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
,	O
mechanical	O
hard	B-Device
disk	I-Device
drives	I-Device
can	O
transfer	O
data	O
at	O
up	O
to	O
524MB/s	O
,	O
which	O
is	O
far	O
beyond	O
the	O
capabilities	O
of	O
the	O
PATA/133	O
specification	O
.	O
</s>
<s>
High-performance	O
solid	B-Device
state	I-Device
drives	I-Device
can	O
transfer	O
data	O
at	O
up	O
to	O
7000	O
–	O
7500MB/s	O
.	O
</s>
<s>
Standard	O
Other	O
names	O
New	O
transfer	O
modes	O
Maximum	O
disk	O
size(512 byte sector )	O
Other	O
significant	O
changes	O
ANSI	O
referenceIDE	O
(	O
pre-ATA	O
)	O
IDE	B-Protocol
PIO	B-General_Concept
0	O
2	O
GiB	O
(	O
2.1	O
GB	O
)	O
22-bit	O
logical	B-Device
block	I-Device
addressing	I-Device
(	O
LBA	O
)	O
–	O
ATA	O
,	O
IDE	B-Protocol
Multi-word	O
DMA	O
0	O
128	O
GiB	O
(	O
137	O
GB	O
)	O
28-bit	O
logical	B-Device
block	I-Device
addressing	I-Device
(	O
LBA	O
)	O
X3.221-1994	O
(	O
obsolete	O
since	O
1999	O
)	O
EIDE	O
,	O
,	O
,	O
PIO	B-General_Concept
3	O
,	O
4Multi-word	O
DMA	O
1	O
,	O
2	O
PCMCIA	B-Architecture
connector	O
.	O
</s>
<s>
X3.279-1996	O
(	O
obsolete	O
since	O
2001	O
)	O
EIDE	O
Single-word	O
DMA	O
modes	O
dropped	O
S.M.A.R.T.	O
,	O
Security	O
,	O
44	O
pin	O
connector	O
for	O
2.5	O
"	O
drives	O
X3.298-1997	O
(	O
obsolete	O
since	O
2002	O
)	O
ATA-4	O
,	O
,	O
also	O
known	O
as	O
UDMA/33	O
AT	B-Protocol
Attachment	I-Protocol
Packet	O
Interface	O
(	O
ATAPI	O
)	O
(	O
support	O
for	O
CD-ROM	B-Device
,	O
tape	O
drives	O
etc	O
.	O
</s>
<s>
)	O
,	O
Optional	O
overlapped	O
and	O
queued	O
command	O
set	O
features	O
,	O
Host	O
Protected	O
Area	O
(	O
HPA	O
)	O
,	O
CompactFlash	B-Device
Association	I-Device
(	O
CFA	O
)	O
feature	O
set	O
for	O
solid	B-Device
state	I-Device
drives	I-Device
NCITS	O
317-1998	O
ATA-5	B-Protocol
,	O
Ultra	O
DMA	O
3	O
,	O
4	O
,	O
also	O
known	O
as	O
UDMA/66	O
80-wire	O
cables	O
;	O
CompactFlash	B-Device
connector	O
NCITS	O
340-2000	O
ATA-6	B-Protocol
,	O
UDMA	O
5	O
,	O
also	O
known	O
as	O
UDMA/100	O
128	O
PiB	O
(	O
144	O
PB	O
)	O
48-bit	O
LBA	O
,	O
Device	O
Configuration	O
Overlay	O
(	O
DCO	O
)	O
,	O
Automatic	O
Acoustic	O
Management	O
(	O
AAM	O
)	O
CHS	B-Device
method	O
of	O
addressing	O
data	O
obsolete	O
NCITS	O
361-2002	O
ATA-7	B-Protocol
,	O
UDMA	O
6	O
,	O
also	O
known	O
as	O
UDMA/133SATA/150	O
SATA	O
1.0	O
,	O
Streaming	O
feature	O
set	O
,	O
long	O
logical/physical	O
sector	O
feature	O
set	O
for	O
non-packet	O
devices	O
ATA-8	O
—	O
Hybrid	B-Device
drive	I-Device
featuring	O
non-volatile	O
cache	B-Device
to	O
speed	O
up	O
critical	O
OS	O
files	O
INCITS	O
452-2008	O
ACS-2	O
—	O
Data	O
Set	O
Management	O
,	O
Extended	O
Power	O
Conditions	O
,	O
CFast	O
,	O
additional	O
stats.	O
,	O
etc	O
.	O
</s>
<s>
ATAPI	O
devices	O
with	O
removable	O
media	O
,	O
other	O
than	O
CD	O
and	O
DVD	O
drives	O
,	O
are	O
classified	O
as	O
ARMD	O
(	O
ATAPI	O
Removable	O
Media	O
Device	O
)	O
and	O
can	O
appear	O
as	O
either	O
a	O
super-floppy	O
(	O
non-partitioned	O
media	O
)	O
or	O
a	O
hard	B-Device
drive	I-Device
(	O
partitioned	O
media	O
)	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
These	O
can	O
be	O
supported	O
as	O
bootable	B-Operating_System
devices	O
by	O
a	O
BIOS	B-Operating_System
complying	O
with	O
the	O
ATAPI	O
Removable	O
Media	O
Device	O
BIOS	B-Operating_System
Specification	O
,	O
originally	O
developed	O
by	O
Compaq	O
Computer	O
Corporation	O
and	O
Phoenix	O
Technologies	O
.	O
</s>
<s>
It	O
specifies	O
provisions	O
in	O
the	O
BIOS	B-Operating_System
of	O
a	O
personal	B-Device
computer	I-Device
to	O
allow	O
the	O
computer	O
to	O
be	O
bootstrapped	B-Operating_System
from	O
devices	O
such	O
as	O
Zip	B-Operating_System
drives	I-Operating_System
,	O
Jaz	B-Device
drives	I-Device
,	O
SuperDisk	B-Device
(	O
LS-120	B-Device
)	O
drives	O
,	O
and	O
similar	O
devices	O
.	O
</s>
<s>
These	O
devices	O
have	O
removable	O
media	O
like	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
but	O
capacities	O
more	O
commensurate	O
with	O
hard	B-Device
drives	I-Device
,	O
and	O
programming	O
requirements	O
unlike	O
either	O
.	O
</s>
<s>
Due	O
to	O
limitations	O
in	O
the	O
floppy	B-Device
controller	O
interface	O
most	O
of	O
these	O
devices	O
were	O
ATAPI	O
devices	O
,	O
connected	O
to	O
one	O
of	O
the	O
host	O
computer	O
's	O
ATA	O
interfaces	O
,	O
similarly	O
to	O
a	O
hard	B-Device
drive	I-Device
or	O
CD-ROM	B-Device
device	O
.	O
</s>
<s>
However	O
,	O
existing	O
BIOS	B-Operating_System
standards	O
did	O
not	O
support	O
these	O
devices	O
.	O
</s>
<s>
An	O
ARMD-compliant	O
BIOS	B-Operating_System
allows	O
these	O
devices	O
to	O
be	O
booted	O
from	O
and	O
used	O
under	O
the	O
operating	B-General_Concept
system	I-General_Concept
without	O
requiring	O
device-specific	O
code	O
in	O
the	O
OS	O
.	O
</s>
<s>
A	O
BIOS	B-Operating_System
implementing	O
ARMD	O
allows	O
the	O
user	O
to	O
include	O
ARMD	O
devices	O
in	O
the	O
boot	B-Operating_System
search	O
order	O
.	O
</s>
<s>
Usually	O
an	O
ARMD	O
device	O
is	O
configured	O
earlier	O
in	O
the	O
boot	B-Operating_System
order	O
than	O
the	O
hard	B-Device
drive	I-Device
.	O
</s>
<s>
Similarly	O
to	O
a	O
floppy	B-Device
drive	I-Device
,	O
if	O
bootable	B-Operating_System
media	O
is	O
present	O
in	O
the	O
ARMD	O
drive	O
,	O
the	O
BIOS	B-Operating_System
will	O
boot	B-Operating_System
from	O
it	O
;	O
if	O
not	O
,	O
the	O
BIOS	B-Operating_System
will	O
continue	O
in	O
the	O
search	O
order	O
,	O
usually	O
with	O
the	O
hard	B-Device
drive	I-Device
last	O
.	O
</s>
<s>
Originally	O
ARMD	O
caused	O
the	O
devices	O
to	O
appear	O
as	O
a	O
sort	O
of	O
very	O
large	O
floppy	B-Device
drive	I-Device
,	O
either	O
the	O
primary	O
floppy	B-Device
drive	I-Device
device	O
00h	O
or	O
the	O
secondary	O
device	O
01h	O
.	O
</s>
<s>
Some	O
operating	B-General_Concept
systems	I-General_Concept
required	O
code	O
changes	O
to	O
support	O
floppy	B-Device
disks	I-Device
with	O
capacities	O
far	O
larger	O
than	O
any	O
standard	O
floppy	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
Also	O
,	O
standard-floppy	O
disk	O
drive	O
emulation	O
proved	O
to	O
be	O
unsuitable	O
for	O
certain	O
high-capacity	B-Device
floppy	I-Device
disk	O
drives	O
such	O
as	O
Iomega	B-Operating_System
Zip	I-Operating_System
drives	I-Operating_System
.	O
</s>
<s>
Later	O
the	O
ARMD-HDD	O
,	O
ARMD-	O
"	O
Hard	B-Device
disk	I-Device
device	O
"	O
,	O
variant	O
was	O
developed	O
to	O
address	O
these	O
issues	O
.	O
</s>
<s>
Under	O
ARMD-HDD	O
,	O
an	O
ARMD	O
device	O
appears	O
to	O
the	O
BIOS	B-Operating_System
and	O
the	O
operating	B-General_Concept
system	I-General_Concept
as	O
a	O
hard	B-Device
drive	I-Device
.	O
</s>
<s>
In	O
August	O
2004	O
,	O
Sam	O
Hopkins	O
and	O
Brantley	O
Coile	O
of	O
Coraid	O
specified	O
a	O
lightweight	O
ATA	B-Protocol
over	I-Protocol
Ethernet	I-Protocol
protocol	O
to	O
carry	O
ATA	O
commands	O
over	O
Ethernet	O
instead	O
of	O
directly	O
connecting	O
them	O
to	O
a	O
PATA	B-Protocol
host	B-Architecture
adapter	I-Architecture
.	O
</s>
<s>
This	O
permitted	O
the	O
established	O
block	O
protocol	O
to	O
be	O
reused	O
in	O
storage	B-General_Concept
area	O
network	O
(	O
SAN	O
)	O
applications	O
.	O
</s>
