<s>
Elan	B-General_Concept
Graphics	I-General_Concept
is	O
a	O
computer	O
graphics	O
architecture	O
for	O
Silicon	O
Graphics	O
computer	B-Device
workstations	I-Device
.	O
</s>
<s>
Elan	B-General_Concept
Graphics	I-General_Concept
was	O
developed	O
in	O
1991	O
and	O
was	O
available	O
as	O
a	O
high-end	O
graphics	O
option	O
on	O
workstations	B-Device
released	O
during	O
the	O
mid-1990s	O
as	O
part	O
of	O
the	O
Express	O
Graphics	O
architectures	O
family	O
.	O
</s>
<s>
Elan	B-General_Concept
Graphics	I-General_Concept
gives	O
the	O
workstation	B-Device
real-time	O
2D	O
and	O
3D	O
graphics	O
rendering	O
capability	O
similar	O
to	O
that	O
of	O
even	O
high-end	O
PCs	B-Device
made	O
over	O
ten	O
years	O
after	O
Elan	O
's	O
introduction	O
,	O
with	O
the	O
exception	O
of	O
texture	O
mapping	O
,	O
which	O
had	O
to	O
be	O
performed	O
in	O
software	O
.	O
</s>
<s>
Together	O
,	O
they	O
are	O
capable	O
of	O
rendering	O
180K	O
Z-buffered	O
,	O
lit	O
,	O
Gouraud-shaded	B-Algorithm
triangles	O
per	O
second	O
.	O
</s>
<s>
The	O
framebuffer	B-Algorithm
has	O
56	O
bits	O
per	O
pixel	O
,	O
causing	O
12-bits	O
per	O
pixel	O
(	O
dithered	O
RGB	O
4/4/4	O
)	O
to	O
be	O
used	O
for	O
a	O
double-buffered	O
,	O
depth	O
buffered	O
,	O
RGB	O
layout	O
.	O
</s>
<s>
Similarly	O
,	O
when	O
Z-buffering	O
is	O
not	O
required	O
,	O
a	O
double-buffered	O
24-bit	O
RGB	O
framebuffer	B-Algorithm
configuration	O
is	O
possible	O
.	O
</s>
<s>
The	O
Elan	B-General_Concept
Graphics	I-General_Concept
system	O
also	O
implemented	O
hardware	O
stencil	O
buffering	O
by	O
allocating	O
4	O
bits	O
from	O
the	O
Z-buffer	O
to	O
produce	O
a	O
combined	O
20-bit	O
Z	O
,	O
4-bit	O
stencil	O
buffer	O
.	O
</s>
<s>
Elan	B-General_Concept
Graphics	I-General_Concept
consists	O
of	O
five	O
graphics	O
subsystems	O
:	O
the	O
HQ2	O
Command	O
Engine	O
,	O
GE7	O
Geometry	O
Subsystem	O
,	O
RE3	O
Raster	O
Engine	O
,	O
VM2	O
framebuffer	B-Algorithm
and	O
VC1	O
Display	O
Subsystem	O
.	O
</s>
<s>
Elan	B-General_Concept
Graphics	I-General_Concept
can	O
produce	O
resolutions	O
up	O
to	O
1280	O
x	O
1024	O
pixels	O
with	O
24-bit	O
color	O
and	O
can	O
also	O
process	O
unencoded	O
NTSC	O
and	O
PAL	B-Language
analog	O
television	O
signals	O
.	O
</s>
<s>
The	O
Elan	B-General_Concept
Graphics	I-General_Concept
system	O
is	O
made	O
up	O
of	O
five	O
daughterboards	O
that	O
plug	O
into	O
the	O
main	O
workstation	B-Device
motherboard	B-Device
.	O
</s>
<s>
The	O
Elan	B-General_Concept
Graphics	I-General_Concept
architecture	O
was	O
superseded	O
by	O
SGI	O
's	O
Extreme	B-General_Concept
Graphics	I-General_Concept
architecture	O
on	O
Indigo2	B-Application
models	O
and	O
eventually	O
by	O
the	O
IMPACT	O
graphics	O
architecture	O
in	O
1995	O
.	O
</s>
