<s>
K42	B-Operating_System
is	O
a	O
discontinued	O
open-source	B-Application
research	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
for	O
cache-coherent	B-General_Concept
64-bit	B-Device
multiprocessor	B-Operating_System
systems	O
.	O
</s>
<s>
The	O
main	O
focus	O
of	O
this	O
OS	O
is	O
to	O
address	O
performance	O
and	O
scalability	B-Architecture
issues	O
of	O
system	B-Application
software	I-Application
on	O
large-scale	O
,	O
shared	B-Operating_System
memory	I-Operating_System
,	O
non-uniform	B-Operating_System
memory	I-Operating_System
access	I-Operating_System
(	O
NUMA	O
)	O
multiprocessing	B-Operating_System
computers	O
.	O
</s>
<s>
K42	B-Operating_System
uses	O
a	O
microkernel	B-Operating_System
architecture	O
rather	O
than	O
the	O
traditional	O
monolithic	B-Operating_System
kernel	I-Operating_System
design	O
.	O
</s>
<s>
K42	B-Operating_System
consists	O
of	O
a	O
small	O
exception-handling	O
component	O
that	O
serves	O
as	O
the	O
microkernel	B-Operating_System
,	O
a	O
fast	O
inter-process	B-Operating_System
communication	I-Operating_System
(	O
IPC	O
)	O
mechanism	O
named	O
protected	B-Operating_System
procedure	I-Operating_System
call	I-Operating_System
(	O
PPC	O
)	O
,	O
and	O
servers	O
for	O
most	O
other	O
components	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
These	O
servers	O
exist	O
in	O
separate	O
address	O
spaces	O
and	O
rely	O
upon	O
the	O
fast	O
IPC	O
mechanism	O
for	O
communication	O
with	O
the	O
microkernel	B-Operating_System
and	O
other	O
servers	O
.	O
</s>
<s>
The	O
core	O
of	O
K42	B-Operating_System
is	O
based	O
on	O
the	O
University	O
of	O
Toronto	O
's	O
operating	B-General_Concept
system	I-General_Concept
Tornado	O
.	O
</s>
<s>
K42	B-Operating_System
is	O
the	O
university	O
's	O
third	O
generation	O
of	O
research	O
on	O
scalable	B-Architecture
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Tornado	O
OS	O
on	O
a	O
nuMachine	B-Device
Multiprocessor	B-Operating_System
was	O
the	O
second	O
generation	O
and	O
Hurricane	O
OS	O
on	O
a	O
Hector	O
Multiprocessor	B-Operating_System
was	O
the	O
first	O
generation	O
.	O
</s>
<s>
K42	B-Operating_System
supports	O
the	O
Linux	B-Application
PowerPC	B-Architecture
64	B-General_Concept
and	O
32	O
application	B-Operating_System
binary	I-Operating_System
interfaces	I-Operating_System
(	O
ABIs	O
)	O
,	O
so	O
most	O
PowerPC	B-Architecture
Linux	B-Application
binary	O
files	O
can	O
run	O
on	O
K42	B-Operating_System
without	O
modification	O
,	O
including	O
the	O
relational	B-Application
database	I-Application
DB2	B-Application
.	O
</s>
<s>
K42	B-Operating_System
has	O
some	O
device	B-Application
drivers	I-Application
implemented	O
specifically	O
for	O
it	O
,	O
but	O
it	O
gets	O
most	O
of	O
its	O
hardware	O
support	O
by	O
directly	O
linking	O
in	O
Linux	B-Application
device	I-Application
drivers	I-Application
to	O
a	O
special	O
server	O
.	O
</s>
<s>
Another	O
goal	O
of	O
the	O
K42	B-Operating_System
design	O
is	O
to	O
achieve	O
a	O
customizable	O
and	O
maintainable	O
system	O
.	O
</s>
<s>
Being	O
built	O
with	O
an	O
object-oriented	B-Language
programming	I-Language
design	O
,	O
it	O
allows	O
applications	O
to	O
customize	O
and	O
thus	O
optimize	O
the	O
OS	O
services	O
required	O
,	O
and	O
then	O
on	O
the	O
fly	O
,	O
hot	B-Device
swap	I-Device
kernel	O
object	O
implementations	O
.	O
</s>
<s>
The	O
K42	B-Operating_System
source	O
is	O
via	O
git	O
:	O
</s>
