for those interested in the 18 Slot Backplane discussed in the "S100 Backplane" thread, please find the attached link below to a .pdf with a schematic and some board prints, im sorry some of the prints arnt of good quality, i had to export as SVG and get to a pdf from there, because kicad wasnt printing the proper track widths, a new problem with the updated software or just user error??.. so the Top Silk Screen image is a little "less sharp", but it will give you the general idea. please note that the board uses the same Active Termination as found on the Compupro Active Terminator and Godbout 10/11/18 slot backplanes. its the same AT used by John Monahan on the S100 board available here. those schematics and documentation along with the original spec sheets from Compupro and Godbout was used as reference to the creation of this board, so full credit to John & Andrew for the running start!
for those who arnt up to speed on this board, the backplane itself (no atx board attached) is a separate board from the ATX board. the kit is 2 (two) boards. one 18-slot backplane board and one ATX PSU board. the backplane board is a "normal" 18-slot active terminated S-100 bus board. The backplane will wire straight up to your +16, -16, +8 and GND power inputs of your S-100 compliant power supply and work as a normal S100 backplane would, you can use it without the ATX board. For all intents and purposes you can throw the ATX board at the cat and forget about it. the backplane board is very similar in design to any other active terminated S-100 bus board. the ATX PSU board however is a separate board that has a 24 pin ATX connector on it (accepting the 20 or 24 pin ATX plug) it has a terminal block output that you 'could' wire up to the input of your S-100 board backplane IF you 1. did not have the need for exactly +16 -16 and +8V. 2. wanted to wire up +5 onto your +8v rail if you ran cards without onboard voltage regulators, 3. could wire up the +12,V -12V, +12V to the "+16, -16, +8v".. please note on this wiring up +12V to the +8V rail is not recommended as your voltage regulators will run hot (it would be best to take the +12v and put it into a high current DC-DC converter to give you +8v). you have the ability to choose what you put on your power rails. It also works prity nice to use your salvaged ATX supply for a lab PSU. the ATX PSU (we could call it a sub-card) has: +12v, +5v, +3.3v, GND & -12v output on its terminal block.
The ATX board uses a small PIC microcontroller to act as the "debounce" switch (on/off) as its about expensive as the amount of 7400 series devices i would have used to put on the board to do the same job. i realize this may cause some "Ahhhhh Errrrrr" for some users.. but the source code or .HEX file, and programmed devices can be supplied if needed.
a point of discussion is the thickness of the board, i realize the current N8VEM 8 slot board uses 3.2mm thickness to make the board very rigid, my biggest concern about this is the ability of the user to use standard S100 connectors that have about a 3mm lead coming out the bottom after the plastic standoff. i would like users to be able to utilize the S100 connectors that some may have been collecting for the last few months. i have added extra mounting holes along the board so there is a mounting hole on either side of every two connectors. currently the PCB house i have sent the design (and use regularly) said 2.0mm was available but not 2.4mm or 3.2mm. current pricing for a 2.0mm board is approximately $31ea for a 10pcs run. i doubt i would like to try and make the board any smaller at this point. but an idea is always to pull off the ATXPSU board and have that manufactured separately if there is not a big demand for it.
i will be taking pre-orders of an initial batch of boards with a Red soldermask once the design has been completed and vetted by the "test group". (or Andrew might like to run it though his Mnufacturer?) this thread is a show of interest and discussion on possible errors and general development. Questions and Comments WELCOME! :-)