<s>
The	O
Netronics	O
Explorer	O
85	O
was	O
an	O
Intel	B-General_Concept
8085	I-General_Concept
based	O
computer	O
produced	O
by	O
Netronics	O
R&D	O
Ltd	O
.	O
located	O
in	O
New	O
Milford	O
,	O
Connecticut	O
between	O
1979	O
and	O
1984	O
.	O
</s>
<s>
Netronics	O
also	O
produced	O
the	O
more	O
well	O
known	O
ELF	B-Device
II	I-Device
computer	O
,	O
and	O
the	O
ill-fated	O
Explorer	O
88	O
computer	O
.	O
</s>
<s>
The	O
Intel	B-General_Concept
8085	I-General_Concept
CPU	B-Device
used	O
a	O
6.144MHz	O
crystal	O
,	O
resulting	O
in	O
the	O
processor	O
operating	O
at	O
3.072MHz	O
.	O
</s>
<s>
The	O
basic	O
system	O
had	O
256	O
bytes	O
of	O
RAM	B-Architecture
and	O
2048	O
bytes	O
of	O
ROM	B-Device
.	O
</s>
<s>
The	O
base	O
system	O
also	O
had	O
cassette	B-Device
tape	I-Device
IO	O
,	O
serial	O
IO	O
which	O
could	O
be	O
configured	O
for	O
RS-232	O
or	O
current	O
loop	O
,	O
and	O
thirty	O
eight	O
bits	O
of	O
parallel	O
IO	O
.	O
</s>
<s>
The	O
system	O
could	O
be	O
expanded	O
to	O
have	O
from	O
two	O
to	O
six	O
S-100	B-Architecture
bus	I-Architecture
sockets	O
.	O
</s>
<s>
Although	O
this	O
computer	O
did	O
have	O
an	O
S-100	B-Architecture
bus	I-Architecture
,	O
it	O
was	O
different	O
from	O
most	O
of	O
its	O
contemporary	O
S-100	B-Architecture
bus	I-Architecture
computers	O
in	O
that	O
it	O
had	O
a	O
large	O
motherboard	B-Device
containing	O
the	O
CPU	B-Device
and	O
associated	O
circuitry	O
,	O
and	O
only	O
two	O
S-100	B-Architecture
bus	I-Architecture
sockets	O
.	O
</s>
<s>
The	O
Sol-20	B-Architecture
computer	O
also	O
had	O
this	O
arrangement	O
.	O
</s>
<s>
The	O
serial	O
data	O
was	O
connected	O
to	O
the	O
Intel	B-General_Concept
8085	I-General_Concept
's	O
SID	O
and	O
SOD	O
(	O
Serial	O
In	O
Data	O
and	O
Serial	O
Out	O
Data	O
)	O
pins	O
.	O
</s>
<s>
This	O
allowed	O
the	O
use	O
of	O
the	O
Intel	B-General_Concept
8085	I-General_Concept
's	O
RIM	O
and	O
SIM	O
instructions	O
to	O
read	O
the	O
level	O
on	O
the	O
SID	O
and	O
set	O
the	O
level	O
on	O
SOD	O
line	O
.	O
</s>
<s>
What	O
was	O
so	O
unique	O
about	O
this	O
implementation	O
was	O
that	O
after	O
resetting	O
the	O
Explorer	O
85	O
,	O
the	O
user	O
had	O
to	O
press	O
the	O
space	O
bar	O
on	O
the	O
attached	O
computer	B-General_Concept
terminal	I-General_Concept
.	O
</s>
<s>
The	O
Explorer	O
85	O
's	O
firmware	O
would	O
measure	O
the	O
time	O
between	O
the	O
start	O
bit	O
and	O
the	O
first	O
data	O
bit	O
in	O
the	O
ASCII	B-Protocol
code	I-Protocol
for	O
the	O
space	O
character	O
.	O
</s>
<s>
Level	O
A	O
was	O
just	O
the	O
motherboard	B-Device
with	O
no	O
S-100	B-Architecture
bus	I-Architecture
sockets	O
loaded	O
.	O
</s>
<s>
This	O
could	O
be	O
ordered	O
with	O
firmware	O
configured	O
for	O
either	O
a	O
computer	B-General_Concept
terminal	I-General_Concept
,	O
or	O
for	O
a	O
hexadecimal	O
keypad	O
which	O
was	O
available	O
from	O
Netronics	O
.	O
</s>
<s>
The	O
Level	O
A	O
motherboard	B-Device
contained	O
a	O
prototyping	O
area	O
,	O
where	O
the	O
user	O
could	O
add	O
circuitry	O
of	O
their	O
own	O
design	O
.	O
</s>
<s>
Level	O
B	O
added	O
the	O
circuitry	O
to	O
drive	O
the	O
two	O
S-100	B-Architecture
bus	I-Architecture
connectors	O
which	O
you	O
could	O
solder	O
into	O
the	O
Level	O
A	O
motherboard	B-Device
.	O
</s>
<s>
This	O
allowed	O
the	O
owner	O
to	O
use	O
any	O
of	O
the	O
myriad	O
of	O
available	O
S-100	B-Architecture
bus	I-Architecture
on	O
the	O
market	O
.	O
</s>
<s>
In	O
1982	O
the	O
Level	O
B	O
upgrade	O
sold	O
for	O
$49.95	O
,	O
and	O
$4.85	O
for	O
each	O
S-100	B-Architecture
bus	I-Architecture
connector	O
.	O
</s>
<s>
Level	O
C	O
was	O
a	O
card	O
cage	O
and	O
S-100	B-Architecture
bus	I-Architecture
expander	O
card	O
.	O
</s>
<s>
This	O
card	O
would	O
plug	O
into	O
one	O
of	O
the	O
S-100	B-Architecture
bus	I-Architecture
sockets	O
on	O
the	O
motherboard	B-Device
.	O
</s>
<s>
You	O
could	O
then	O
plug	O
up	O
to	O
five	O
more	O
S-100	B-Architecture
bus	I-Architecture
cards	O
into	O
the	O
expander	O
card	O
.	O
</s>
<s>
One	O
of	O
the	O
two	O
original	O
slots	O
on	O
the	O
motherboard	B-Device
was	O
still	O
available	O
for	O
use	O
,	O
giving	O
the	O
Level	O
C	O
Explorer	O
85	O
a	O
capacity	O
of	O
six	O
S-100	B-Architecture
bus	I-Architecture
cards	O
.	O
</s>
<s>
In	O
1982	O
the	O
Level	O
C	O
upgrade	O
sold	O
for	O
$39.95	O
,	O
and	O
$4.85	O
for	O
each	O
S-100	B-Architecture
bus	I-Architecture
connector	O
.	O
</s>
<s>
Level	O
D	O
was	O
a	O
RAM	B-Architecture
upgrade	O
.	O
</s>
<s>
This	O
could	O
take	O
the	O
form	O
of	O
up	O
to	O
4k	O
of	O
RAM	B-Architecture
on	O
the	O
motherboard	B-Device
,	O
or	O
Netronics	O
S-100	O
Jaws	O
memory	O
board	O
.	O
</s>
<s>
The	O
Jaws	O
memory	O
board	O
used	O
from	O
eight	O
to	O
thirty	O
two	O
4116	O
16k	O
by	O
1	O
bit	O
dynamic	O
random	B-Architecture
access	I-Architecture
memory	I-Architecture
chips	O
,	O
which	O
could	O
be	O
added	O
in	O
groups	O
of	O
eight	O
.	O
</s>
<s>
The	O
Jaws	O
memory	O
board	O
used	O
an	O
Intel	O
8202	O
dynamic	O
random	B-Architecture
access	I-Architecture
memory	I-Architecture
controller	O
chip	O
to	O
refresh	O
the	O
memory	O
,	O
and	O
multiplex	O
the	O
address	O
bits	O
.	O
</s>
<s>
In	O
1982	O
the	O
Level	O
D	O
upgrade	O
sold	O
for	O
as	O
little	O
as	O
$49.95	O
for	O
the	O
4k	O
motherboard	B-Device
upgrade	O
,	O
to	O
as	O
much	O
as	O
$299.95	O
for	O
the	O
64k	O
Jaws	O
upgrade	O
.	O
</s>
<s>
Level	O
E	O
activated	O
the	O
ROM	B-Device
sockets	O
in	O
the	O
motherboard	B-Device
.	O
</s>
<s>
This	O
allowed	O
the	O
user	O
to	O
put	O
custom	O
programs	O
in	O
the	O
ROM	B-Device
socket	O
,	O
or	O
the	O
user	O
could	O
purchase	O
a	O
Microsoft	O
ROM	B-Device
BASIC	O
interpreter	O
from	O
Netronics	O
.	O
</s>
<s>
The	O
Microsoft	O
ROM	B-Device
BASIC	O
could	O
store	O
and	O
load	O
programs	O
using	O
a	O
cassette	B-Device
tape	I-Device
recorder	I-Device
.	O
</s>
