<s>
MBus	B-Architecture
is	O
a	O
computer	B-General_Concept
bus	I-General_Concept
designed	O
and	O
implemented	O
by	O
Sun	O
Microsystems	O
for	O
communication	O
between	O
high	O
speed	O
computer	O
system	O
components	O
,	O
such	O
as	O
the	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
,	O
motherboard	B-Device
and	O
main	O
memory	O
.	O
</s>
<s>
SBus	B-Architecture
is	O
used	O
in	O
the	O
same	O
machines	O
to	O
connect	O
add-on	O
cards	O
to	O
the	O
motherboard	B-Device
.	O
</s>
<s>
MBus	B-Architecture
was	O
first	O
used	O
in	O
Sun	O
's	O
first	O
multiprocessor	B-Operating_System
SPARC-based	O
system	O
,	O
the	O
SPARCserver600MP	O
series	O
(	O
launched	O
in	O
1991	O
)	O
,	O
and	O
later	O
found	O
use	O
in	O
the	O
SPARCstation	B-Architecture
10	I-Architecture
and	O
SPARCstation	B-Architecture
20	I-Architecture
workstations	O
.	O
</s>
<s>
The	O
bus	O
permits	O
the	O
integration	O
of	O
several	O
microprocessors	O
on	O
a	O
single	O
motherboard	B-Device
,	O
in	O
a	O
multiprocessing	B-Operating_System
configuration	O
with	O
up	O
to	O
eight	O
CPUs	B-Device
packaged	O
in	O
detachable	O
MBus	B-Architecture
modules	O
.	O
</s>
<s>
In	O
practice	O
,	O
the	O
number	O
of	O
processors	O
per	O
MBus	B-Architecture
is	O
limited	O
to	O
four	O
.	O
</s>
<s>
Single	O
processor	O
systems	O
were	O
also	O
sold	O
that	O
use	O
the	O
MBus	B-Architecture
protocol	O
internally	O
,	O
but	O
with	O
the	O
CPUs	B-Device
permanently	O
attached	O
to	O
the	O
motherboard	B-Device
to	O
lower	O
manufacturing	O
costs	O
.	O
</s>
<s>
MBus	B-Architecture
specifies	O
a	O
64-bit	B-Device
datapath	B-General_Concept
,	O
which	O
uses	O
36-bit	O
physical	O
addressing	O
,	O
giving	O
an	O
address	B-General_Concept
space	I-General_Concept
of	O
64	O
GB	O
.	O
</s>
<s>
XBus	B-Architecture
is	O
a	O
packet-switched	O
bus	O
used	O
in	O
the	O
SPARCserver	B-Device
1000	O
,	O
SPARCcenter	B-Device
2000	O
and	O
Cray	B-Device
CS6400	I-Device
.	O
</s>
<s>
This	O
corresponds	O
to	O
the	O
circuit-switched	O
MBus	B-Architecture
,	O
with	O
identical	O
electrical	O
characteristics	O
and	O
physical	O
form	O
factor	O
but	O
an	O
incompatible	O
signalling	O
protocol	O
.	O
</s>
<s>
KBus	B-Architecture
is	O
a	O
high-speed	O
interconnection	O
system	O
for	O
linking	O
multiple	O
MBuses	O
,	O
used	O
in	O
Solbourne	O
Computer	O
Series	O
6	O
and	O
Series	O
7	O
computer	O
systems	O
.	O
</s>
<s>
The	O
MBus	B-Architecture
standard	O
was	O
cooperatively	O
developed	O
by	O
Sun	O
and	O
Ross	O
Technology	O
and	O
released	O
in	O
1991	O
.	O
</s>
<s>
Manufacturers	O
who	O
produced	O
computer	O
systems	O
using	O
the	O
MBus	B-Architecture
included	O
Sun	O
,	O
Ross	O
Technology	O
,	O
Hyundai/Axil	O
,	O
Fujitsu	O
,	O
Solbourne	O
Computer	O
,	O
Tatung	O
,	O
GCS	O
,	O
Auspex	O
,	O
ITRI	O
,	O
ICL	O
,	O
Cray	O
,	O
Amdahl	O
,	O
Themis	O
,	O
DTK	O
and	O
Kamstrup	O
.	O
</s>
