Configuring the Processor Tech 3P+S as an IMSAI SIO-2

[glitch]

link: http://www.glitchwrks.com/2018/08/30/3ps-imsai-sio

I recently repaired a Processor Tech 3P+S I/O board for the VCFed Museum. This 3P+S is going in an IMSAI, so it was to be configured as compatible with the first channel of an IMSAI SIO-2. The 3P+S is a super versatile I/O board, much of the configuration is left to the user to jumper in as they want, but making it look like an IMSAI SIO-2 did require a cut-and-jump. But, after fixing the control/data register ordering and taking the bitrate base clock from the 2 MHz pin (pin 49 on S-100) instead of the system clock, it works! I was able to pull my IMSAI SIO-2, drop in this modified 3P+S, and run the software I'd been running on the SIO-2.

The 3P+S is on my short list for "S-100 boards to reproduce." It's a very handy serial interface, being as how it can be made to look like most other manufacturers' boards.

 

[Corey986]

I'm wondering if you even should do a 1:1 reproduction.

I would think take the schematic and re-lay the board out so that you can use dip switches instead of the jumpers so that the card can be quickly reconfigured. This way you can quickly emulate different boards without the pain of re-wiring.

 

[glitch]

I'm wondering if you even should do a 1:1 reproduction.

I would think take the schematic and re-lay the board out so that you can use dip switches instead of the jumpers so that the card can be quickly reconfigured. This way you can quickly emulate different boards without the pain of re-wiring.

I don't think you could reasonably provide for all of the configuration possibilities with DIP switches. Boards on which I plan on changing the configuration often get machine pin socket pins for all locations instead of direct soldering, both to reduce stresses on the board and to make reconfiguration faster.

If I were to lay out the board from scratch, I'd also change a lot of component choices, expansion connectors, etc. It wouldn't be much like a 3P+S at the end

 

[Corey986]

I do agree on the pin sockets. All my 3P+S use them, but it’s still a pain pulling little jumper wires and and pushing them in.

 

[glitch]

I do agree on the pin sockets. All my 3P+S use them, but it’s still a pain pulling little jumper wires and and pushing them in.

Another plus of having reproduction boards: much more available *and* affordable! That's a big part of why I did the SSM IO-2 reproduction, I was running out of old boards to strip down for new projects.