<s>
pSOS	B-Operating_System
(	O
Portable	O
Software	O
On	O
Silicon	O
)	O
is	O
a	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
RTOS	B-Operating_System
)	O
,	O
created	O
in	O
about	O
1982	O
by	O
Alfred	O
Chao	O
,	O
and	O
developed	O
and	O
marketed	O
for	O
the	O
first	O
part	O
of	O
its	O
life	O
by	O
his	O
company	O
Software	O
Components	O
Group	O
(	O
SCG	O
)	O
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
pSOS	B-Operating_System
rapidly	O
became	O
the	O
RTOS	B-Operating_System
of	O
choice	O
for	O
all	O
embedded	B-Architecture
systems	I-Architecture
based	O
on	O
the	O
Motorola	B-Device
68000	I-Device
series	I-Device
family	O
architecture	O
,	O
because	O
it	O
was	O
written	O
in	O
68000	O
assembly	B-Language
language	I-Language
and	O
was	O
highly	O
optimised	O
from	O
the	O
start	O
.	O
</s>
<s>
It	O
was	O
also	O
modularised	O
,	O
with	O
early	O
support	O
for	O
OS-aware	O
debugging	O
,	O
plug-in	O
device	B-Application
drivers	I-Application
,	O
Internet	B-Protocol
protocol	I-Protocol
suite	I-Protocol
(	O
TCP/IP	B-Protocol
)	O
stacks	O
,	O
language	O
libraries	B-Library
,	O
and	O
disk	O
subsystems	O
.	O
</s>
<s>
Later	O
came	O
source	O
code	O
level	O
debugging	O
,	O
multiprocessing	B-Operating_System
support	O
,	O
and	O
further	O
computer	B-Architecture
networking	I-Architecture
extensions	O
.	O
</s>
<s>
In	O
about	O
1991	O
,	O
Software	O
Components	O
Group	O
was	O
acquired	O
by	O
Integrated	O
Systems	O
Inc	O
.	O
(	O
ISI	O
)	O
which	O
further	O
developed	O
pSOS	B-Operating_System
,	O
then	O
renamed	O
as	O
pSOS+	B-Operating_System
,	O
for	O
other	O
microprocessor	O
families	O
,	O
by	O
rewriting	O
most	O
of	O
it	O
in	O
the	O
programming	B-Language
language	I-Language
C	I-Language
.	O
Attention	O
was	O
also	O
paid	O
to	O
supporting	O
successively	O
more	O
integrated	B-Application
development	I-Application
environments	I-Application
,	O
culminating	O
in	O
pRISM+	O
.	O
</s>
<s>
In	O
July	O
1994	O
,	O
ISI	O
acquired	O
Digital	O
Research	O
's	O
modular	O
real-time	B-Operating_System
multi-tasking	O
operating	O
system	O
FlexOS	B-Operating_System
from	O
Novell	O
.	O
</s>
<s>
In	O
1995	O
,	O
ISI	O
offered	O
a	O
pSOSystem/NEST	O
package	O
for	O
Novell	B-Application
Embedded	I-Application
Systems	I-Application
Technology	I-Application
(	O
NEST	B-Application
)	O
.	O
</s>
<s>
In	O
February	O
2000	O
,	O
ISI	O
was	O
acquired	O
by	O
Wind	O
River	O
Systems	O
,	O
the	O
originators	O
of	O
the	O
rival	O
RTOS	B-Operating_System
VxWorks	B-Operating_System
.	O
</s>
<s>
Despite	O
initial	O
reports	O
that	O
pSOS	B-Operating_System
support	O
would	O
continue	O
,	O
development	O
was	O
halted	O
.	O
</s>
<s>
Wind	O
River	O
announced	O
plans	O
for	O
a	O
'	O
convergence	O
 '	O
version	O
of	O
VxWorks	B-Operating_System
which	O
will	O
support	O
pSOS	B-Operating_System
system	O
calls	O
,	O
and	O
that	O
no	O
further	O
releases	O
of	O
pSOS	B-Operating_System
will	O
occur	O
.	O
</s>
<s>
NXP	O
Semiconductors	O
acquired	O
pSOS	B-Operating_System
for	O
TriMedia	B-General_Concept
from	O
Wind	O
River	O
and	O
continued	O
to	O
support	O
this	O
OS	O
for	O
the	O
TriMedia	B-General_Concept
very	B-General_Concept
long	I-General_Concept
instruction	I-General_Concept
word	I-General_Concept
(	O
VLIW	B-General_Concept
)	O
core	O
.	O
</s>
<s>
In	O
March	O
2000	O
,	O
rival	O
company	O
Express	B-Operating_System
Logic	I-Operating_System
released	O
their	O
Evaluation	O
Kit	O
for	O
pSOS+	B-Operating_System
users	O
,	O
designed	O
to	O
provide	O
a	O
migration	O
path	O
to	O
its	O
ThreadX	B-Operating_System
RTOS	B-Operating_System
.	O
</s>
<s>
During	O
August	O
2000	O
,	O
MapuSoft	O
Technologies	O
Inc	O
.	O
came	O
up	O
with	O
the	O
pSOS	B-Operating_System
OS	O
Changer	O
porting	O
kit	O
which	O
can	O
smoothly	O
move	O
the	O
software	O
to	O
multiple	O
OS	O
such	O
as	O
Linux	B-Application
,	O
VxWorks	B-Operating_System
,	O
and	O
more	O
.	O
</s>
<s>
It	O
includes	O
an	O
integrated	B-Application
development	I-Application
environment	I-Application
(	O
IDE	O
)	O
and	O
application	O
programming	O
interface	O
(	O
API	B-General_Concept
)	O
optimization	O
along	O
with	O
a	O
profiling	O
tool	O
to	O
measure	O
API	B-General_Concept
timing	O
on	O
target	O
boards	O
(	O
www.mapusoft.com	O
)	O
.	O
</s>
<s>
In	O
August	O
2007	O
,	O
RoweBots	O
,	O
a	O
former	O
partner	O
of	O
SCG	O
and	O
ISI	O
,	O
open	O
sourced	O
their	O
pSOS+	B-Operating_System
compatible	O
version	O
called	O
Reliant	O
.	O
</s>
<s>
The	O
Xenomai	B-Operating_System
project	O
supports	O
pSOS+	B-Operating_System
APIs	B-General_Concept
(	O
and	O
others	O
traditional	O
RTOS	B-Operating_System
APIs	B-General_Concept
)	O
over	O
a	O
Linux-based	O
real-time	B-Operating_System
framework	O
to	O
allow	O
existing	O
industrial	O
applications	O
to	O
migrate	O
easily	O
to	O
a	O
Linux-based	O
environment	O
while	O
keeping	O
stringent	O
real-time	B-Operating_System
guarantees	O
.	O
</s>
<s>
Another	O
open	O
sourced	O
alternative	O
is	O
RTEMS	B-Operating_System
,	O
which	O
has	O
support	O
for	O
various	O
APIs	B-General_Concept
,	O
including	O
the	O
"	O
Classic	O
API	B-General_Concept
"	O
(	O
compatible	O
to	O
pSOS	B-Operating_System
)	O
and	O
the	O
POSIX	O
API	B-General_Concept
.	O
</s>
<s>
Compared	O
to	O
Linux	B-Application
,	O
RTEMS	B-Operating_System
is	O
a	O
closer	O
match	O
to	O
pSOS	B-Operating_System
applications	O
due	O
to	O
its	O
lower	O
memory	O
size	O
and	O
its	O
strict	O
realtime	O
behaviour	O
.	O
</s>
<s>
Popular	O
Secure	B-Protocol
Sockets	I-Protocol
Layer	I-Protocol
(	O
SSL	O
)	O
,	O
now	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
,	O
libraries	B-Library
such	O
as	O
wolfSSL	B-Protocol
still	O
support	O
pSOS	B-Operating_System
.	O
</s>
