<s>
Xsgi	B-Architecture
is	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
(	O
X11	B-Operating_System
)	O
server	O
for	O
the	O
IRIX-based	O
graphical	O
workstations	O
and	O
servers	O
from	O
Silicon	O
Graphics	O
(	O
SGI	O
)	O
.	O
</s>
<s>
Xsgi	B-Architecture
was	O
released	O
in	O
1991	O
with	O
IRIX	B-Operating_System
4.0	O
on	O
the	O
SGI	B-Device
Indigo	I-Device
workstation	O
.	O
</s>
<s>
Work	O
on	O
Xsgi	B-Architecture
began	O
in	O
May	O
1989	O
when	O
Tom	O
Paquin	O
left	O
IBM	O
to	O
join	O
SGI	O
to	O
integrate	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
with	O
SGI	O
's	O
IRIS	B-Library
GL	I-Library
interface	O
.	O
</s>
<s>
Paquin	O
recruited	O
a	O
set	O
of	O
software	O
engineers	O
experienced	O
in	O
X	B-Operating_System
server	O
implementation	O
:	O
Jeff	O
Weinstein	O
,	O
Erik	O
Fortune	O
,	O
Paul	O
Shupak	O
,	O
John	O
Giannandrea	O
,	O
Peter	O
Daifuku	O
,	O
Michael	O
Toy	O
,	O
Todd	O
Newman	O
,	O
Spence	O
Murray	O
,	O
and	O
Dave	O
Spalding	O
.	O
</s>
<s>
This	O
makes	O
the	O
Monochrome	O
FrameBuffer	O
(	O
MFB	O
)	O
and	O
Color	O
FrameBuffer	O
(	O
CFB	O
)	O
device-dependent	O
rendering	O
layers	O
supplied	O
with	O
the	O
MIT	O
X11	B-Operating_System
Sampler	O
Server	O
inappropriate	O
for	O
Silicon	O
Graphics	O
hardware	O
.	O
</s>
<s>
SCO	O
later	O
incorporated	O
the	O
NFB	O
layer	O
in	O
its	O
X	B-Operating_System
server	O
porting	O
layer	O
.	O
</s>
<s>
Silicon	O
Graphics	O
hardware	O
includes	O
overlay	O
planes	O
to	O
provide	O
a	O
hardware	B-Architecture
overlay	I-Architecture
.	O
</s>
<s>
Initial	O
efforts	O
by	O
Todd	O
Newman	O
to	O
implement	O
overlay	O
plane	O
support	O
in	O
Xsgi	B-Architecture
eventually	O
led	O
to	O
Peter	O
Daifuku	O
's	O
"	O
fully	O
functional	O
"	O
support	O
for	O
overlay	O
planes	O
.	O
</s>
<s>
The	O
previous	O
MIT	O
X	B-Operating_System
sample	O
server	O
treats	O
these	O
two	O
clipping	O
regions	O
as	O
being	O
the	O
identical	O
region	O
.	O
</s>
<s>
Xsgi	B-Architecture
advertises	O
overlay	O
planes	O
as	O
X11	B-Operating_System
visuals	O
with	O
their	O
overlay	O
characteristics	O
described	O
by	O
the	O
convention	O
.	O
</s>
<s>
Erik	O
Fortune	O
developed	O
the	O
X	B-Application
keyboard	I-Application
extension	I-Application
(	O
XKB	B-Application
)	O
for	O
Xsgi	B-Architecture
.	O
</s>
<s>
Xsgi	B-Architecture
supports	O
the	O
X11	B-Operating_System
,	O
IRIS	B-Library
GL	I-Library
,	O
OpenGL	B-Application
,	O
Display	O
PostScript	O
,	O
and	O
PEX	O
PHIGS	B-Library
rendering	O
models	O
.	O
</s>
