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S-100 Front Panel (Bus Monitor) project


Veteran Member
Dec 21, 2006
Hi! Here is a quick update on the S-100 System Monitor Board project. The second round of prototype PCBs for the base board and display mezzanines are built and tested. There were some corrections to all the boards but I think we've got it now. I will be ordering manufactured PCBs in the near future. What remains is to update the trace routing on the SMB base board and display mezzanines and then place the order.

Functionally the S-100 SMB is like an updated version of the Jade Bus Probe extended to S-100/IEEE-696 8 and 16 bit modes. The Jade Bus Probe is a useful board for debugging a broken system or to get a working system up and running and I think the S-100 SMB will be too. Sadly the Jade Bus Probe is essentially extinct and only very rarely do units become available -- maybe once every couple of years or so. When they do surface on eBay, they'll reliably fetch more than $200 regardless of condition and bid competition will be strong. Its hard to say anything about JBP statistics though since they are so rarely available.

The S-100 SMB is quite complicated and requires *TWO* PCBs to operate; the S-100 SMB base board which looks like a typical S-100 board, and the display mezzanines which can optionally connect to the base board and contain the displays (LED bars, HP5082-7340s, or TIL311s) and various mode switches (run/stop, reset, etc).

If you would like to get in on the initial order, please let me know soonest to get on the waiting list. I'd like to get quantity up to a level that I can keep the PCB unit cost reasonable. My target cost is $20 for the base board and $20 for the 3 display mezzanines. The 3 display mezzanines come as a single PCB the builder cuts themselves using a saw or razor blade. I estimate to need order about 30 units of each to reach target unit costs.

Since this is an initial manufactured PCB order, there is always some risk of finding "issues" with the board. However, after two rounds of internal prototype PCBs I think we've probably hammered out the really big bugs and we know the board *does* work. There may be additional discoveries once testing spreads to a broader range of systems. If that is a concern you can wait for later rounds of manufactured PCBs however there is no guarrantee there will be other rounds or when they would happen. If there are other round of PCBs it will be a minimum of several *months* before it happens as both John and I would like to move on to other S-100 boards and projects. PCB respins and reorders are lower priority compared to developing new boards and tend to be delayed.

So that's the state of affairs with the S-100 SMB board project. Please consider and take under advisement. As always, "Caveat Emptor" as per all home brew computing activities. I don't recommend this project as suitable for first time builders for a number of reasons.

Thanks and have a nice day!

Andrew Lynch