<s>
TOPS	B-Device
(	O
Transcendental	O
OPerating	O
System	O
)	O
is	O
a	O
peer-to-peer	O
LAN-based	O
file	O
sharing	O
system	O
best	O
known	O
in	O
its	O
Macintosh	B-Device
implementation	O
,	O
but	O
also	O
available	O
for	O
DOS	B-Device
and	O
able	O
to	O
interoperate	O
with	O
Unix	O
's	O
NFS	B-Protocol
.	O
</s>
<s>
Originally	O
written	O
by	O
Centram	O
Systems	O
West	O
,	O
the	O
company	O
was	O
purchased	O
by	O
Sun	O
Microsystems	O
as	O
part	O
of	O
Sun	O
's	O
development	O
of	O
the	O
NFS	B-Protocol
ecosystem	O
.	O
</s>
<s>
The	O
Centram	O
company	O
was	O
renamed	O
to	O
TOPS	B-Device
after	O
its	O
acquisition	O
by	O
Sun	O
.	O
</s>
<s>
Sales	O
of	O
TOPS	B-Device
dried	O
up	O
after	O
the	O
introduction	O
of	O
System	B-Operating_System
7	I-Operating_System
,	O
which	O
featured	O
a	O
similar	O
file	O
sharing	O
system	O
built-in	O
,	O
and	O
Sun	O
spun	O
off	O
their	O
NFS	B-Protocol
developments	O
to	O
Sitka	O
.	O
</s>
<s>
TOPS	B-Device
was	O
implemented	O
in	O
the	O
1980s	O
,	O
an	O
era	O
where	O
each	O
computer	O
system	O
featured	O
its	O
own	O
networking	O
protocol	O
and	O
were	O
generally	O
unable	O
to	O
talk	O
to	O
each	O
other	O
.	O
</s>
<s>
At	O
the	O
time	O
Apple	O
was	O
in	O
the	O
midst	O
of	O
the	O
Macintosh	B-Device
Office	I-Device
effort	O
,	O
and	O
was	O
working	O
with	O
two	O
external	O
companies	O
to	O
develop	O
the	O
Apple	B-Protocol
Filing	I-Protocol
Protocol	I-Protocol
(	O
AFP	O
)	O
,	O
built	O
on	O
top	O
of	O
AppleTalk	B-Application
.	O
</s>
<s>
The	O
Macintosh	B-Device
Office	I-Device
effort	O
ultimately	O
failed	O
,	O
and	O
one	O
of	O
the	O
two	O
companies	O
,	O
Centram	O
,	O
decided	O
to	O
implement	O
a	O
similar	O
system	O
on	O
their	O
own	O
.	O
</s>
<s>
This	O
became	O
the	O
first	O
version	O
of	O
TOPS	B-Device
.	O
</s>
<s>
When	O
TOPS	B-Device
was	O
originally	O
released	O
in	O
July	O
1985	O
there	O
was	O
no	O
peer-to-peer	O
file	O
sharing	O
solution	O
on	O
the	O
Mac	O
.	O
</s>
<s>
According	O
to	O
PC	O
Magazine	O
,	O
connecting	O
a	O
Mac	O
to	O
an	O
Apple	O
LaserWriter	O
printer	O
was	O
the	O
initial	O
intended	O
function	O
of	O
AppleTalk	B-Application
.	O
</s>
<s>
Apple	O
's	O
own	O
file	O
sharing	O
solution	O
,	O
AppleShare	B-General_Concept
,	O
was	O
not	O
released	O
until	O
later	O
,	O
and	O
unlike	O
TOPS	B-Device
it	O
required	O
a	O
dedicated	O
server	O
machine	O
to	O
run	O
on	O
,	O
at	O
least	O
a	O
Mac	B-Device
Plus	I-Device
.	O
</s>
<s>
For	O
smaller	O
offices	O
TOPS	B-Device
was	O
an	O
attractive	O
low-cost	O
solution	O
,	O
and	O
saw	O
relatively	O
widespread	O
use	O
.	O
</s>
<s>
Even	O
after	O
the	O
introduction	O
of	O
AppleShare	B-General_Concept
,	O
TOPS	B-Device
managed	O
to	O
hold	O
on	O
to	O
an	O
estimated	O
600,000	O
client	O
installs	O
.	O
</s>
<s>
TOPS	B-Device
was	O
initially	O
a	O
protocol	O
using	O
a	O
custom	O
set	O
of	O
remote	B-Operating_System
procedure	I-Operating_System
calls	I-Operating_System
and	O
able	O
to	O
talk	O
only	O
between	O
TOPS	B-Device
clients	O
.	O
</s>
<s>
PCs	O
generally	O
lacked	O
networking	O
of	O
any	O
sort	O
,	O
and	O
Centram	O
addressed	O
this	O
problem	O
by	O
introducing	O
a	O
line	O
of	O
LocalTalk	B-Device
cards	O
for	O
the	O
PC	O
,	O
along	O
with	O
a	O
TOPS	B-Device
client	O
.	O
</s>
<s>
Centram	O
later	O
introduced	O
the	O
"	O
FlashTalk	O
"	O
networking	O
system	O
that	O
used	O
external	O
clocking	O
to	O
improve	O
LocalTalk	B-Device
performance	O
.	O
</s>
<s>
The	O
Zilog	B-Device
SCC	I-Device
powering	O
the	O
serial	B-Protocol
ports	I-Protocol
on	O
the	O
Mac	O
used	O
an	O
internal	O
3.6864MHz	O
clock	O
that	O
could	O
then	O
be	O
divided	O
down	O
to	O
provide	O
different	O
standard	O
bit	O
rates	O
.	O
</s>
<s>
The	O
fastest	O
rate	O
available	O
internally	O
was	O
230.4kbit/s	O
,	O
used	O
by	O
LocalTalk	B-Device
.	O
</s>
<s>
However	O
,	O
the	O
system	O
also	O
allowed	O
the	O
clock	O
to	O
be	O
read	O
from	O
a	O
pin	O
in	O
the	O
serial	B-Protocol
port	I-Protocol
,	O
giving	O
rise	O
to	O
the	O
possibility	O
of	O
faster	O
speeds	O
with	O
the	O
right	O
external	O
equipment	O
.	O
</s>
<s>
FlashTalk	O
combined	O
a	O
conventional	O
LocalTalk-like	O
dongle	O
with	O
a	O
clocking	O
source	O
and	O
an	O
external	O
power	O
supply	O
.	O
</s>
<s>
Using	O
these	O
connectors	O
,	O
and	O
the	O
associated	O
software	O
,	O
TOPS	B-Device
could	O
run	O
at	O
770kbit/s	O
.	O
</s>
<s>
This	O
was	O
not	O
only	O
a	O
fairly	O
dramatic	O
improvement	O
over	O
LocalTalk	B-Device
,	O
but	O
also	O
relatively	O
speedy	O
overall	O
in	O
an	O
era	O
when	O
1Mbit/s	O
networks	O
were	O
still	O
common	O
.	O
</s>
<s>
After	O
the	O
Sun	O
purchase	O
in	O
April	O
1987	O
,	O
TOPS	B-Device
was	O
given	O
the	O
problem	O
of	O
making	O
a	O
client	O
that	O
could	O
also	O
access	O
Sun	O
file	O
shares	O
using	O
NFS	B-Protocol
.	O
</s>
<s>
Centram	O
solved	O
this	O
problem	O
by	O
porting	O
their	O
file	O
sharing	O
protocol	O
to	O
TCP/IP	B-Protocol
.	O
</s>
<s>
This	O
was	O
not	O
trivial	O
;	O
neither	O
Mac	O
OS	O
nor	O
Windows	O
supported	O
TCP/IP	B-Protocol
"	O
out	O
of	O
the	O
box	O
"	O
,	O
so	O
what	O
was	O
now	O
the	O
TOPS	B-Device
Division	O
of	O
Sun	O
had	O
to	O
write	O
a	O
complete	O
IP	B-Protocol
stack	I-Protocol
for	O
the	O
Mac	O
and	O
Windows	O
.	O
</s>
<s>
Centram	O
had	O
already	O
written	O
such	O
a	O
stack	O
for	O
their	O
"	O
TOPS	B-Device
Terminal	O
"	O
,	O
a	O
freeware	B-License
(	O
but	O
not	O
open	B-License
source	I-License
)	O
Telnet	B-Protocol
terminal	O
for	O
the	O
Mac	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
majority	O
of	O
Macintosh	B-Device
systems	O
used	O
LocalTalk	B-Device
(	O
or	O
PhoneNet	B-Protocol
)	O
for	O
connectivity	O
,	O
and	O
could	O
not	O
be	O
directly	O
connected	O
to	O
the	O
Ethernet-based	O
Unix	O
LANs	B-General_Concept
.	O
</s>
<s>
They	O
worked	O
around	O
this	O
problem	O
by	O
supporting	O
an	O
emerging	O
LocalTalk-to-Ethernet	O
bridging	B-Protocol
standard	O
known	O
as	O
"	O
KIP	O
"	O
,	O
short	O
for	O
Kinetics	O
Internet	O
Protocol	O
.	O
</s>
<s>
KIP	O
encapsulated	O
TCP/IP	B-Protocol
packets	O
inside	O
AppleTalk	B-Application
packets	O
,	O
allowing	O
them	O
to	O
be	O
sent	O
over	O
existing	O
LocalTalk	B-Device
connections	O
.	O
</s>
<s>
Dedicated	O
KIP-supporting	O
network	B-Protocol
bridges	I-Protocol
were	O
available	O
that	O
stripped	O
off	O
the	O
AppleTalk	B-Application
packaging	O
,	O
re-formed	O
the	O
IP	O
packets	O
inside	O
,	O
and	O
sent	O
them	O
out	O
over	O
Ethernet	O
.	O
</s>
<s>
One	O
limitation	O
of	O
the	O
TCP	B-Protocol
stack	I-Protocol
was	O
that	O
it	O
did	O
not	O
support	O
DNS	B-Protocol
,	O
requiring	O
users	O
to	O
type	O
in	O
IP	O
addresses	O
of	O
the	O
peers	O
they	O
wanted	O
to	O
communicate	O
with	O
.	O
</s>
<s>
In	O
a	O
network	O
of	O
mostly	O
Macs	O
or	O
Windows	O
PCs	O
this	O
was	O
not	O
an	O
issue	O
,	O
as	O
DNS	B-Protocol
was	O
not	O
widely	O
used	O
with	O
these	O
systems	O
at	O
that	O
time	O
.	O
</s>
<s>
KIP	O
also	O
reduced	O
the	O
need	O
for	O
DNS	B-Protocol
,	O
as	O
it	O
allowed	O
a	O
Mac	O
's	O
existing	O
Address	O
Resolution	O
Protocol	O
(	O
AARP	O
)	O
code	O
within	O
AppleTalk	B-Application
to	O
look	O
up	O
the	O
AppleTalk	B-Application
address	O
of	O
the	O
remote	O
peer	O
,	O
and	O
then	O
communicate	O
with	O
the	O
TOPS	B-Device
stack	O
on	O
that	O
machine	O
to	O
find	O
the	O
corresponding	O
IP	O
address	O
.	O
</s>
<s>
TOPS	B-Device
also	O
added	O
the	O
new	O
"	O
InBox	O
Personal	O
Connection	O
"	O
e-mail	O
system	O
,	O
first	O
developed	O
by	O
Symantec	O
.	O
</s>
<s>
TOPS	B-Device
 '	O
attractiveness	O
was	O
seriously	O
eroded	O
with	O
the	O
introduction	O
of	O
System	B-Operating_System
7	I-Operating_System
in	O
1991	O
.	O
</s>
<s>
TOPS	B-Device
had	O
initially	O
competed	O
against	O
the	O
dedicated-server	O
AppleShare	B-General_Concept
,	O
but	O
System	B-Operating_System
7	I-Operating_System
included	O
a	O
file	O
sharing	O
server	O
built-in	O
,	O
one	O
that	O
proved	O
to	O
be	O
much	O
faster	O
than	O
then-current	O
versions	O
of	O
TOPS	B-Device
.	O
</s>
<s>
TOPS	B-Device
sales	O
dwindled	O
and	O
Sun	O
spun	O
off	O
the	O
division	O
as	O
Sitka	O
,	O
before	O
closing	O
it	O
entirely	O
in	O
1993	O
.	O
</s>
