<s>
GD-ROM	B-Device
(	O
an	O
abbreviation	O
of	O
"	O
Gigabyte	O
Disc	O
Read-Only	B-Device
Memory	I-Device
"	O
)	O
is	O
a	O
proprietary	O
optical	B-Device
disc	I-Device
format	O
originally	O
used	O
for	O
the	B-Operating_System
Dreamcast	I-Operating_System
video	O
game	O
console	O
,	O
as	O
well	O
as	O
its	O
arcade	O
counterpart	O
,	O
the	O
Sega	O
NAOMI	O
and	O
select	O
Triforce	B-Device
arcade	O
board	O
titles	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
Yamaha	O
to	O
curb	O
piracy	O
common	O
to	O
standard	O
CDs	B-Device
and	O
to	O
offer	O
increased	O
storage	O
capacity	O
without	O
the	O
expense	O
of	O
the	O
fledgling	O
DVD-ROM	O
.	O
</s>
<s>
It	O
is	O
similar	O
to	O
the	O
standard	O
CD-ROM	B-Device
except	O
that	O
the	O
pits	O
on	O
the	O
disc	O
are	O
packed	O
more	O
closely	O
together	O
,	O
resulting	O
in	O
a	O
higher	O
storage	O
capacity	O
of	O
1	O
gigabyte	O
,	O
a	O
42%	O
increase	O
over	O
a	O
conventional	O
CD	B-Device
's	O
capacity	O
of	O
700	O
megabytes	O
.	O
</s>
<s>
The	B-Operating_System
Dreamcast	I-Operating_System
ended	O
up	O
being	O
the	O
only	O
sixth-generation	O
console	O
with	O
a	O
disc	O
based	O
on	O
CD	B-Device
technology	O
rather	O
than	O
DVD	O
technology	O
;	O
even	O
the	O
Nintendo	B-Application
GameCube	I-Application
's	O
smaller	O
8	O
cm	O
discs	O
held	O
50%	O
more	O
data	O
due	O
to	O
being	O
based	O
on	O
DVD	O
technology	O
.	O
</s>
<s>
In	O
addition	O
,	O
GD-ROM	B-Device
proved	O
to	O
be	O
an	O
ineffective	O
anti-piracy	O
measure	O
when	O
it	O
was	O
discovered	O
the	B-Operating_System
Dreamcast	I-Operating_System
's	O
forgotten	O
MIL-CD	O
functionality	O
could	O
be	O
exploited	O
to	O
boot	O
games	O
burned	O
to	O
CD	B-Device
albeit	O
with	O
some	O
content	O
removed	O
.	O
</s>
<s>
After	O
the	O
discontinuation	O
of	O
the	B-Operating_System
Dreamcast	I-Operating_System
worldwide	O
on	O
March	O
31	O
,	O
2001	O
,	O
Sega	O
continued	O
to	O
use	O
the	O
GD-ROM	B-Device
format	O
in	O
arcades	O
with	O
the	O
Sega	O
NAOMI	O
2	O
,	O
Triforce	B-Device
and	O
Sega	O
Chihiro	O
.	O
</s>
<s>
The	O
last	O
disc-based	O
Naomi	O
2	O
and	O
Triforce	B-Device
games	O
were	O
released	O
in	O
2006	O
which	O
marked	O
the	O
final	O
releases	O
using	O
the	O
GD-ROM	B-Device
format	O
.	O
</s>
<s>
The	O
format	O
was	O
developed	O
for	O
Sega	O
by	O
Yamaha	O
,	O
and	O
first	O
commercially	O
appeared	O
with	O
the	B-Operating_System
Dreamcast	I-Operating_System
's	O
Japanese	O
launch	O
in	O
November	O
1998	O
.	O
</s>
<s>
GD-ROM	B-Device
was	O
created	O
because	O
the	O
standard	O
CD-ROM	B-Device
was	O
prone	O
to	O
piracy	O
and	O
reaching	O
the	O
limits	O
of	O
its	O
storage	O
capacity	O
,	O
while	O
implementing	O
the	O
then	O
brand-new	O
DVD-ROM	O
technology	O
would	O
have	O
made	O
console	O
production	O
too	O
costly	O
.	O
</s>
<s>
However	O
,	O
the	B-Operating_System
Dreamcast	I-Operating_System
did	O
retain	O
the	O
ability	O
to	O
read	O
standard	O
CD-ROM	B-Device
discs	O
,	O
and	O
thus	O
still	O
suffered	O
from	O
software	O
piracy	O
as	O
bootleggers	O
managed	O
to	O
fit	O
certain	O
games	O
on	O
CDs	B-Device
and	O
exploit	O
the	B-Operating_System
Dreamcast	I-Operating_System
console	O
's	O
compatibility	O
with	O
the	O
MIL-CD	O
format	O
.	O
</s>
<s>
As	O
the	O
GD-ROM	B-Device
format	O
can	O
hold	O
about	O
of	O
data	O
,	O
illegally	O
copying	O
Dreamcast	B-Operating_System
games	O
onto	O
a	O
CD-ROM	B-Device
sometimes	O
required	O
the	O
removal	O
of	O
certain	O
game	O
features	O
,	O
although	O
this	O
did	O
not	O
prevent	O
piracy	O
.	O
</s>
<s>
The	O
main	O
difference	O
between	O
GD-ROM	B-Device
and	O
MIL-CD	O
is	O
that	O
MIL-CD	O
can	O
boot	O
on	O
an	O
unmodified	O
Dreamcast	B-Operating_System
like	O
original	O
SEGA	O
's	O
disk	O
,	O
making	O
piracy	O
extremely	O
easy	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
1999	O
Sega	O
released	O
a	O
new	O
revision	O
of	O
the	B-Operating_System
Dreamcast	I-Operating_System
hardware	O
which	O
was	O
not	O
able	O
to	O
boot	O
MIL-CDs	O
,	O
therefore	O
preventing	O
piracy	O
.	O
</s>
<s>
Before	O
the	B-Operating_System
Dreamcast	I-Operating_System
was	O
released	O
,	O
Sega	O
"	O
confirmed	O
that	O
Dreamcast	B-Operating_System
owners	O
will	O
one	O
day	O
be	O
able	O
to	O
upgrade	O
the	O
GD-ROM	B-Device
drive	O
to	O
DVD	O
,	O
"	O
as	O
information	O
indicated	O
Sony	O
's	O
upcoming	O
PlayStation	B-Device
2	I-Device
would	O
use	O
the	O
DVD	O
format	O
with	O
its	O
much	O
larger	O
capacity	O
4.7	O
GB	O
single-layered	O
up	O
to	O
8.5	O
GB	O
double-layered	O
discs	O
compared	O
to	O
the	O
1	O
GB	O
capacity	O
of	O
the	O
GD-ROM	B-Device
.	O
</s>
<s>
Despite	O
displaying	O
a	O
Dreamcast	B-Operating_System
DVD	O
display	O
unit	O
at	O
E3	O
2000	O
,	O
the	O
plans	O
for	O
a	O
DVD	O
add-on	O
or	O
fully	O
separate	O
unit	O
never	O
materialized	O
during	O
the	O
short	O
production	O
run	O
of	O
the	B-Operating_System
Dreamcast	I-Operating_System
.	O
</s>
<s>
GD-ROM	B-Device
was	O
also	O
made	O
available	O
as	O
an	O
upgrade	O
for	O
the	B-Operating_System
Dreamcast	I-Operating_System
's	O
arcade	O
cousin	O
,	O
Sega	O
NAOMI	O
and	O
the	O
later	O
Sega	O
NAOMI	O
2	O
,	O
providing	O
alternate	O
media	O
to	O
its	O
cartridge-based	O
software	O
.	O
</s>
<s>
It	O
is	O
also	O
used	O
as	O
an	O
option	O
on	O
both	O
the	O
Sega	O
Chihiro	O
and	O
Triforce	B-Device
.	O
</s>
<s>
There	O
are	O
three	O
data	O
areas	O
on	O
a	O
GD-ROM	B-Device
disc	O
.	O
</s>
<s>
The	O
first	O
is	O
in	O
conventional	O
CD	B-Device
format	O
,	O
and	O
usually	O
contains	O
an	O
audio	O
track	O
with	O
a	O
warning	O
that	O
the	O
disc	O
is	O
for	O
use	O
on	O
a	O
Dreamcast	B-Operating_System
,	O
and	O
can	O
damage	O
CD	B-Device
players	I-Device
.	O
</s>
<s>
The	O
CD	B-Device
section	O
also	O
contains	O
a	O
data	O
segment	O
,	O
which	O
is	O
only	O
readable	O
in	O
PCs	O
.	O
</s>
<s>
Although	O
most	O
discs	O
include	O
only	O
text	O
files	O
identifying	O
the	O
game	O
,	O
its	O
copyright	O
and	O
bibliography	O
,	O
some	O
contain	O
bonus	O
material	O
for	O
home	O
computer	O
users	O
(	O
for	O
example	O
,	O
Sonic	B-Application
Adventure	I-Application
contains	O
images	O
of	O
Sonic	O
characters	O
to	O
use	O
on	O
the	O
desktop	O
)	O
.	O
</s>
<s>
There	O
then	O
follows	O
a	O
separator	O
track	O
which	O
contains	O
no	O
data	O
except	O
for	O
the	O
text	O
Produced	O
by	O
or	O
under	O
license	O
from	O
Sega	O
Enterprises	O
LTD	O
Trademark	O
Sega	O
(	O
Similar	O
to	O
the	O
Sega	B-Device
Saturn	I-Device
,	O
it	O
was	O
believed	O
that	O
the	O
security	O
key	O
was	O
stored	O
in	O
this	O
area	O
to	O
prevent	O
piracy	O
)	O
.	O
</s>
<s>
A	O
normal	O
CD-reader	O
will	O
not	O
read	O
beyond	O
the	O
first	O
track	O
because	O
,	O
according	O
to	O
the	O
CD	B-Device
table	B-Application
of	I-Application
contents	I-Application
(	O
TOC	B-Application
)	O
,	O
there	O
is	O
no	O
data	O
there	O
.	O
</s>
<s>
With	O
modified	O
firmware	B-Application
on	O
a	O
few	O
optical	O
drive	O
models	O
that	O
looks	O
for	O
a	O
second	O
TOC	B-Application
in	O
the	O
high-density	O
region	O
it	O
is	O
possible	O
to	O
read	O
data	O
from	O
the	O
high-density	O
region	O
.	O
</s>
<s>
One	O
can	O
also	O
utilize	O
a	O
"	O
swap-trick	O
"	O
by	O
first	O
letting	O
the	O
CD-reader	O
read	O
the	O
TOC	B-Application
from	O
an	O
audio	O
CD	B-Device
with	O
a	O
special	O
99	O
minute	O
TOC	B-Application
and	O
then	O
swapping	O
that	O
disc	O
with	O
a	O
GD-ROM	B-Device
in	O
a	O
way	O
that	O
avoids	O
alerting	O
the	O
CD-reader	O
that	O
a	O
new	O
disc	O
has	O
been	O
inserted	O
.	O
</s>
<s>
It	O
is	O
then	O
possible	O
to	O
read	O
as	O
much	O
data	O
from	O
the	O
high-density	O
region	O
as	O
indicated	O
by	O
the	O
TOC	B-Application
from	O
the	O
first	O
disc	O
.	O
</s>
<s>
The	O
most	O
popular	O
way	O
to	O
access	O
data	O
from	O
GD-ROMs	B-Device
,	O
however	O
,	O
is	O
to	O
use	O
the	B-Operating_System
Dreamcast	I-Operating_System
itself	O
as	O
a	O
drive	O
,	O
and	O
copy	O
the	O
data	O
to	O
a	O
computer	O
by	O
means	O
of	O
a	O
"	O
coder	O
's	O
cable	O
"	O
or	O
a	O
Dreamcast	B-Operating_System
Broadband	O
Adapter	O
.	O
</s>
<s>
Another	O
alternative	O
is	O
modding	O
the	B-Operating_System
Dreamcast	I-Operating_System
to	O
add	O
a	O
USB	O
connector	O
.	O
</s>
<s>
Sega	O
has	O
discontinued	O
production	O
of	O
GD-ROM	B-Device
media	O
.	O
</s>
<s>
The	O
second	O
section	O
(	O
in	O
conventional	O
CD	B-Device
format	O
)	O
usually	O
contains	O
a	O
message	O
informing	O
users	O
that	O
the	O
disc	O
can	O
damage	O
AV	O
equipment	O
.	O
</s>
<s>
This	O
is	O
possible	O
because	O
a	O
CD	B-Device
player	I-Device
can	O
interpret	O
the	O
game	O
data	O
track	O
as	O
an	O
audio	O
track	O
,	O
which	O
will	O
result	O
in	O
loud	O
noise	O
being	O
played	O
through	O
the	O
speakers	O
.	O
</s>
<s>
NTSC-U	O
discs	O
usually	O
contain	O
the	O
message	O
,	O
"	O
Warning	O
:	O
This	O
disc	O
is	O
only	O
for	O
use	O
on	O
Sega	B-Operating_System
Dreamcast	I-Operating_System
.	O
</s>
<s>
or	O
"	O
This	O
is	O
a	O
Dreamcast	B-Operating_System
game	O
disc	O
.	O
</s>
<s>
Some	O
discs	O
contain	O
light-hearted	O
or	O
humorous	O
messages	O
from	O
the	O
game	O
's	O
characters	O
(	O
for	O
example	O
,	O
Skies	B-Device
of	I-Device
Arcadia	I-Device
gives	O
the	O
message	O
,	O
"	O
We	O
ca	O
n't	O
save	O
the	O
world	O
from	O
a	O
CD	B-Device
player	I-Device
,	O
so	O
just	O
put	O
us	O
back	O
in	O
the	B-Operating_System
Dreamcast	I-Operating_System
so	O
we	O
can	O
do	O
our	O
job	O
!	O
"	O
)	O
.	O
</s>
<s>
PAL	O
region	O
discs	O
contain	O
the	O
message	O
,	O
"	O
This	O
is	O
a	O
Dreamcast	B-Operating_System
disc	O
,	O
and	O
is	O
for	O
use	O
only	O
on	O
a	O
Dreamcast	B-Operating_System
unit	O
.	O
</s>
<s>
The	O
GD-ROM	B-Device
in	O
the	B-Operating_System
Dreamcast	I-Operating_System
works	O
in	O
constant	B-Device
angular	I-Device
velocity	I-Device
(	O
CAV	O
)	O
mode	O
,	O
like	O
the	O
majority	O
of	O
modern	O
optical	O
drives	O
.	O
</s>
<s>
Very	O
old	O
CD-ROM	B-Device
drives	O
read	O
with	O
a	O
constant	B-Device
linear	I-Device
velocity	I-Device
(	O
CLV	O
)	O
design	O
,	O
however	O
(	O
usually	O
12×	O
or	O
slower	O
)	O
.	O
</s>
<s>
Sega	O
achieved	O
the	O
higher	O
density	O
by	O
decreasing	O
the	O
speed	O
of	O
the	O
disc	O
to	O
half	O
and	O
by	O
letting	O
the	O
standard	O
CD-ROM	B-Device
components	O
read	O
at	O
the	O
normal	O
rate	O
thus	O
nearly	O
doubling	O
the	O
disc	O
's	O
data	O
density	O
.	O
</s>
<s>
This	O
method	O
allowed	O
Sega	O
to	O
use	O
cheaper	O
off-the-shelf	O
components	O
when	O
building	O
the	B-Operating_System
Dreamcast	I-Operating_System
.	O
</s>
<s>
The	O
NetBSD	B-Device
project	O
has	O
developed	O
a	O
GDRom	B-Device
driver	O
for	O
NetBSD	B-Device
.	O
</s>
<s>
A	O
port	O
of	O
that	O
driver	O
for	O
Linux	B-Operating_System
exists	O
,	O
though	O
due	O
to	O
licensing	O
issues	O
and	O
the	O
poor	O
compatibility	O
of	O
that	O
driver	O
with	O
Linux	B-Operating_System
kernel	I-Operating_System
interfaces	O
,	O
a	O
new	O
Linux	B-Operating_System
driver	O
is	O
under	O
development	O
.	O
</s>
<s>
Linux	O
kernel	O
2.6.25	O
comes	O
with	O
support	O
for	O
the	O
GD-ROM	B-Device
drive	O
on	O
the	B-Operating_System
Dreamcast	I-Operating_System
.	O
</s>
