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A new version of the S100Computers Serial IO Board


Experienced Member
Oct 19, 2008
San Ramon, CA
Back towards the end of 2020 Damian Wildie in Australia showed us that you could very nicely run Cromemco's Cromix-Plus with the S100Computers 68030 CPU board in the S100 bus. He provided details that should allow users to do the same. He ran into one problem however, the S100Computers Serial IO board did not work well as the operating systems console. It tended to drop keyboard input characters. Damian went on to show that the board could be modified using some spare gates on the board to make it work.

There was also an issue that Cromix utilizes a clock timer tick to track time and other things. He utilized the crude 555 timer interrupt on the S100Computers System Monitor board to generate an interrupt. It works but such a setup is not accurate and drifts.

The Serial IO board (V3.1) has been around 2010. It has shown itself to be very popular and reliable. It is now overdue a few tweaks and improvements however. I have used that board as a basis for a new version (V4.2) to incorporate proper serial port S100 bus interrupts and S100 bus processing of the INTA signal to the onboard Zilog Z8530 UART. Also a "proper" EML440 1Hz timer chip has been added as well some other minor changes

The board is described here:-

http://s100computers.com/My System Pages/Serial IO B oard/Serial%20IO%20Board.htm#Serial%20IO%20Board%20V4.2

I am now going to have a batch of these boards made by PCBCart (China) and I am opening it up for users here that may like to obtain one or two boards.

By now the process should be familiar to most users. The bare boards (depending on the number requested) will probably cost ~$20/board + shipping. This will be payable via PayPal AFTER you receive the board(s). If you would like one or two boards indicate by a response here:-


Do not e-mail me directly. I use this group forum tread to track orders. Turnaround will probably be about 1 month.

John Monahan