Building a BA08 for a pdp8/L

Chris Zach cz at
Wed Jan 19 22:07:51 CST 2022

So now that my pdp8/L is up and running (it now has a serial port and 
runs FOCAL69 quite well) I'm thinking about the next step, which is of 
course more memory.

This requires a BA08 or BM8/L or something expansion box but to be 
honest I have enough spare flip chips and such from the wrecked 8/I to 
build about 3 core memory systems. So given that the schematics for the 
BA08 are online, they look pretty darn simple, I have the parts, and I 
have the parts does anyone know if it's possible to get a flip chip 
backplane to work on and wire up to emulate a BA08?

It looks like they just used the data break interface lines to hook up 
to the processor. Everything's there, Memory address bus, memory data 
bus, and the various signals for jumps and the like that could allow one 
to decode and implement the extra instructions needed.

Hm. Might just be easier to build it with an FPGA or something as it's 
mostly linking up simple gates and the whole core memory section could 
be removed by a 4k*12 memory array. Anyone ever done this?


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