The Netronics Explorer 85 was an Intel 8085 based computer produced by Netronics R&D Ltd. located in New Milford, Connecticut between 1979 and 1984.
Netronics also produced the more well known ELF II computer, and the ill fated Explorer 88.
Although this computer did have an S-100 bus, it was different from most of contemporary S-100 bus computers. The difference is the large motherboard containing
CPU and associated circuity, and only two S-100 bus sockets. Sol-20 computer also had this arrangement.
Another unique feature of this computer was its serial port. The serial data was connected to the Intel 8085's SID and SOD
(Serial In Data and Serial Out Data) pins. This allowed the use of the Intel 8085's RIM and SIM instructions to read the level on the SID and
set the level on SOD line. What was so unique about this implementation was that after reseting the Explorer 85,
the user had to press the space bar on the attached computer terminal. The Explorer 85's firmware would measure the time between the start bit and
the first data bit in the ASCII code for the space character. This allowed the Explorer 85 to automatically calculate and match the baud rate of the terminal.
The down side of this technique was that the firmware needed to be in a loop monitoring the level on the SID pin to receive data from the terminal.
If the processor was doing some other task when the user pressed a key on the terminal, that data would be lost.
In addition to having a reset button on the front of the computer, the Explorer 85 had an interrupt button. This allow the user to interrupt a locked up
program and return to the debugger, without reseting the computer and losing all of their work.
Explorer 85 was sold in five configuretions:
Level A was just the motherboard with no S-100 bus sockets loaded. This could be ordered with firmware configured for either a computer terminal,
or for a hexadecimal keypad which was available from Netronics. The Level A configuration did not include a power supply. Level A motherboard contained a
prototyping area, where the user could add circuitry of their own design.
Level B added the circuitry to drive the two S-100 bus connectors which you could solder into the Level A motherboard.
Level C had added S-100 bus card cage with 5 extra slots.
Level D had 4 KB of RAM on motherboard
Level E had activated ROM sockets on motherboard for custom ROMs.