<s>
The	O
QCDOC	B-Operating_System
(	O
quantum	O
chromodynamics	O
on	O
a	O
chip	O
)	O
is	O
a	O
supercomputer	B-Architecture
technology	O
focusing	O
on	O
using	O
relatively	O
cheap	O
low	O
power	O
processing	B-Architecture
elements	I-Architecture
to	O
produce	O
a	O
massively	B-Operating_System
parallel	I-Operating_System
machine	O
.	O
</s>
<s>
The	O
purpose	O
of	O
the	O
collaboration	O
was	O
to	O
exploit	O
computing	O
facilities	O
for	O
lattice	O
field	O
theory	O
calculations	O
whose	O
primary	O
aim	O
is	O
to	O
increase	O
the	O
predictive	O
power	O
of	O
the	O
Standard	B-General_Concept
Model	I-General_Concept
of	O
elementary	O
particle	O
interactions	O
through	O
numerical	O
simulation	O
of	O
quantum	O
chromodynamics	O
(	O
QCD	O
)	O
.	O
</s>
<s>
The	O
target	O
was	O
to	O
build	O
a	O
massively	B-Operating_System
parallel	I-Operating_System
supercomputer	B-Architecture
able	O
to	O
peak	O
at	O
10	O
Tflops	O
with	O
sustained	O
power	O
at	O
50%	O
capacity	O
.	O
</s>
<s>
There	O
are	O
three	O
QCDOCs	B-Operating_System
in	O
service	O
each	O
reaching	O
10	O
Tflops	O
peak	O
operation	O
.	O
</s>
<s>
University	O
of	O
Edinburgh	O
's	O
Parallel	O
Computing	O
Centre	O
(	O
EPCC	B-Device
)	O
.	O
</s>
<s>
QCDOC	B-Operating_System
was	O
to	O
replace	O
an	O
earlier	O
design	O
,	O
QCDSP	O
,	O
where	O
the	O
power	O
came	O
from	O
connecting	O
large	O
amounts	O
of	O
DSPs	B-Architecture
together	O
in	O
a	O
similar	O
fashion	O
.	O
</s>
<s>
QCDOC	B-Operating_System
can	O
be	O
seen	O
as	O
a	O
predecessor	O
to	O
the	O
highly	O
successful	O
Blue	B-Operating_System
Gene/L	I-Operating_System
supercomputer	B-Architecture
.	O
</s>
<s>
Blue	B-Operating_System
Gene	I-Operating_System
is	O
also	O
a	O
massively	B-Operating_System
parallel	I-Operating_System
supercomputer	B-Architecture
built	O
with	O
a	O
large	O
amount	O
of	O
cheap	O
,	O
relatively	O
weak	O
PowerPC	O
440	O
based	O
SoC	B-Architecture
nodes	O
connected	O
with	O
a	O
high	O
bandwidth	O
multidimensional	O
mesh	O
.	O
</s>
<s>
Each	O
node	O
has	O
one	O
DIMM	B-General_Concept
socket	O
capable	O
of	O
holding	O
between	O
128	O
and	O
2048	O
MB	O
of	O
333MHz	O
ECC	O
DDR	O
SDRAM	O
.	O
</s>
<s>
Each	O
of	O
these	O
24	O
channels	O
has	O
DMA	B-General_Concept
to	O
the	O
other	O
nodes	O
 '	O
on-chip	O
DRAM	O
or	O
the	O
external	O
SDRAM	O
.	O
</s>
<s>
Two	O
nodes	O
are	O
placed	O
together	O
on	O
a	O
daughter	O
card	O
with	O
one	O
DIMM	B-General_Concept
socket	O
and	O
a	O
4:1	O
Ethernet	O
hub	O
for	O
off-card	O
communications	O
.	O
</s>
<s>
The	O
QCDOC	B-Operating_System
runs	O
a	O
custom-built	O
operating	O
system	O
,	O
QOS	O
,	O
which	O
facilitates	O
boot	O
,	O
runtime	O
,	O
monitoring	O
,	O
diagnostics	O
,	O
and	O
performance	O
and	O
simplifies	O
management	O
of	O
the	O
large	O
number	O
of	O
computing	O
nodes	O
.	O
</s>
<s>
It	O
uses	O
a	O
custom	O
embedded	O
kernel	B-Operating_System
and	O
provides	O
single	O
process	O
POSIX	O
(	O
"	O
unix-like	O
"	O
)	O
compatibility	O
using	O
the	O
Cygnus	O
newlib	B-Language
library	O
.	O
</s>
<s>
The	O
kernel	B-Operating_System
includes	O
a	O
specially	O
written	O
UDP/IP	B-Protocol
stack	O
and	O
NFS	B-Protocol
client	O
for	O
disk	O
access	O
.	O
</s>
<s>
Any	O
multitasking	O
is	O
scheduled	O
by	O
the	O
host	O
controller	O
system	O
which	O
is	O
a	O
regular	O
computer	O
using	O
a	O
large	O
amounts	O
of	O
Ethernet	O
ports	O
connecting	O
to	O
the	O
QCDOC	B-Operating_System
.	O
</s>
