<s>
Fireplane	B-Architecture
is	O
a	O
computer	O
internal	O
interconnect	B-General_Concept
created	O
by	O
Sun	O
Microsystems	O
.	O
</s>
<s>
The	O
Fireplane	B-Architecture
interconnect	B-General_Concept
architecture	O
is	O
an	O
evolutionary	O
development	O
of	O
Sun	O
's	O
previous	O
Ultra	B-Architecture
Port	I-Architecture
Architecture	I-Architecture
(	O
UPA	O
)	O
.	O
</s>
<s>
It	O
was	O
introduced	O
in	O
October	O
2000	O
as	O
the	O
processor	O
I/O	O
interconnect	B-General_Concept
in	O
the	O
Sun	B-Architecture
Blade	I-Architecture
1000	I-Architecture
workstation	B-Device
,	O
followed	O
in	O
early	O
2001	O
by	O
its	O
use	O
in	O
the	O
Sun	B-Architecture
Fire	I-Architecture
and	O
Sun	B-Architecture
Fire	I-Architecture
15K	I-Architecture
series	O
enterprise	B-Application
servers	I-Application
.	O
</s>
<s>
These	O
coincided	O
with	O
the	O
popular	O
expansion	O
of	O
the	O
web	O
in	O
the	O
dot	O
com	O
boom	O
and	O
a	O
shift	O
of	O
Sun	O
's	O
main	O
market	O
from	O
Unix	B-Device
workstations	I-Device
to	O
datacenter	B-Operating_System
servers	O
such	O
as	O
the	O
Starfire	B-Device
,	O
supporting	O
high	O
traffic	O
web	O
sites	O
.	O
</s>
<s>
Peak	O
performance	O
(	O
in	O
the	O
Sun	B-Architecture
Blade	I-Architecture
1000	I-Architecture
)	O
reached	O
67.2	O
GBytes/second	O
or	O
a	O
sustained	O
9.6	O
Gbit/s	O
(	O
2.4	O
Gbit/s	O
for	O
each	O
processor	O
)	O
.	O
</s>
<s>
Each	O
generation	O
of	O
Sun	O
architecture	O
had	O
involved	O
upgraded	O
processors	O
and	O
matching	O
upgrades	O
to	O
the	O
bus	O
or	O
interconnect	B-General_Concept
architectures	O
that	O
supported	O
them	O
.	O
</s>
<s>
Multiprocessors	B-Operating_System
,	O
shared	B-Operating_System
memory	I-Operating_System
,	O
memory	B-General_Concept
caching	I-General_Concept
and	O
switching	B-Operating_System
between	I-Operating_System
CPU	I-Operating_System
and	I-Operating_System
memory	I-Operating_System
were	O
technologies	O
necessary	O
to	O
achieve	O
this	O
.	O
</s>
<s>
The	O
Sun	B-Architecture
Fire	I-Architecture
15K	I-Architecture
series	O
frame	O
allows	O
18	O
combined	O
processor	O
and	O
memory	O
expander	O
boards	O
.	O
</s>
<s>
The	O
Fireplane	B-Architecture
interconnect	B-General_Concept
uses	O
18×18	O
crossbar	O
switches	O
to	O
connect	O
between	O
them	O
.	O
</s>
<s>
Overall	O
peak	O
bandwidth	O
through	O
the	O
interconnect	B-General_Concept
is	O
43	O
Gbytes	O
per	O
second	O
.	O
</s>
<s>
As	O
memory	O
architectures	O
increase	O
in	O
complexity	O
,	O
maintaining	O
cache	B-General_Concept
coherence	I-General_Concept
becomes	O
a	O
greater	O
problem	O
than	O
simple	O
connectivity	O
.	O
</s>
<s>
Fireplane	B-Architecture
represents	O
a	O
substantial	O
advance	O
over	O
previous	O
interconnects	B-General_Concept
in	O
this	O
aspect	O
.	O
</s>
<s>
It	O
combines	O
both	O
snoopy	B-General_Concept
cache	I-General_Concept
and	O
point-to-point	O
directory-based	O
models	O
to	O
give	O
a	O
two-level	O
cache	B-General_Concept
coherence	I-General_Concept
model	O
.	O
</s>
<s>
Fireplane	B-Architecture
combines	O
both	O
,	O
to	O
give	O
a	O
scalable	O
shared	B-Operating_System
memory	I-Operating_System
architecture	I-Operating_System
.	O
</s>
<s>
Each	O
expander	O
board	O
implements	O
snooping	O
across	O
the	O
board	O
,	O
with	O
directory	O
coherence	O
across	O
the	O
interconnect	B-General_Concept
.	O
</s>
<s>
Small	O
to	O
mid-sized	O
Fireplane	B-Architecture
systems	O
,	O
up	O
to	O
24	O
processors	O
,	O
use	O
a	O
single	O
coherence	O
domain	O
.	O
</s>
<s>
Larger	O
systems	O
with	O
more	O
processors	O
use	O
multiple	O
coherence	O
domains	O
across	O
their	O
backplane	O
interconnect	B-General_Concept
.	O
</s>
<s>
Competing	O
systems	O
from	O
makers	O
such	O
as	O
SGI	O
or	O
the	O
HP	B-Device
Superdome	I-Device
series	O
use	O
only	O
a	O
single	O
level	O
of	O
coherency	O
support	O
and	O
so	O
require	O
the	O
more	O
complex	O
directory	O
coherence	O
to	O
be	O
used	O
throughout	O
.	O
</s>
<s>
Fireplane	B-Architecture
used	O
for	O
smaller	O
servers	O
and	O
workstations	B-Device
is	O
optimised	O
for	O
their	O
single	O
domain	O
performance	O
.	O
</s>
