yes we used to at computer exchange inc... we had a bunch of blank I/o boards with the i/o special chips traces on the corner of board we would populate that portion then built out the rest..... rest of board was like a prototype board I scored a stack of them at a san jose computer junk show one time. we have voice synth that would plug into ho using natl. digitaker chip set built onto one of these i/o proto boards.... they were all gold plated etc.... which I still have some... we do have the first talker we built though ... if you score some of these boards most of the startup of the project is taken care of! ed# _www.smecc.org_ (http://www.smecc.org) In a message dated 8/2/2016 2:10:16 P.M. US Mountain Standard Time, perlpowers at gmail.com writes: On another note, has anyone ever tried making their own I/O boards for any of the 2100 series computers? The closest I found was http://newton.freehostia.com/hp/ where he makes a paper tape emulator and disk interface. However both of those are designed to connect to an existing I/O board like the "microcircuit interface". I haven't seen anything yet on how to interface to the I/O bus, but then again there are thousands of pages of manuals still to browse through.