<s>
The	O
New	O
York	O
University	O
's	O
Ultracomputer	B-Operating_System
is	O
a	O
significant	O
processor	O
design	O
in	O
the	O
history	O
of	O
parallel	B-Operating_System
computing	I-Operating_System
.	O
</s>
<s>
The	O
system	O
supported	O
an	O
innovative	O
fetch-and-add	B-Operating_System
process	O
coordination	O
instruction	O
,	O
and	O
the	O
custom	O
VLSI	O
network	O
switches	O
could	O
combine	O
references	O
(	O
including	O
fetch-and-adds	B-Operating_System
)	O
from	O
several	O
processors	O
into	O
a	O
single	O
reference	O
,	O
to	O
reduce	O
memory	O
contention	O
.	O
</s>
<s>
Most	O
of	O
the	O
work	O
done	O
was	O
theoretical	O
,	O
but	O
two	O
prototypes	B-Application
were	O
built	O
:	O
</s>
<s>
A	O
16-processor	O
,	O
16	O
memory-module	O
machine	O
with	O
custom	O
VLSI	O
switches	O
supporting	O
the	O
fetch-and-add	B-Operating_System
instruction	O
.	O
</s>
<s>
Ultracomputer	B-Operating_System
technology	O
was	O
the	O
basis	O
for	O
the	O
IBM	O
Research	O
Research	O
Parallel	B-Operating_System
Processor	I-Operating_System
Prototype	B-Application
(	O
RP3	O
)	O
,	O
an	O
experimental	O
parallel	B-Operating_System
computer	I-Operating_System
that	O
supported	O
512	O
processing	O
nodes	O
.	O
</s>
