Goal: a (very) low cost full replica of the PDP-8/I.
Design: use a Raspberry Pi, a custom front panel PCB to mount it behind, and 26 nice-to-use toggle switches. Extend the simh emulator to drive the front panel.
Reason: PDP-8 replicas can get very expensive very quickly. The idea was to do the exact opposite: design a faithful replica using minimum parts. Made possible by the fact that the computing engine is available for <$30 (Pi) and in software, there's no better replica of PDP-8 functionality than the simh emulator.
Result: Pi drives the 92 leds and 26 switches using a multiplexing process running in parallel to the simh emulator. Only a few ARM instructions are necessary to update the front panel during a PDP instruction cycle. An acrylic front panel faithfully reproduces that of the original.
Project progress & details on my web site.