Issue 3 added the VIA chip - Versatile Interface Adapter R6522. It provides two serial ports, two 16bits counters / timers and a shift register for parallel-to-serial conversion and vice versa.

Unfortunatelly, Issue 3 has an error - ground was not connected together and there were missing place for the resonant capacitor and load, so some CPUs won't work. You can solder one wire and a two parts directly to the PCB, but it is not a solution, so I designed an Issue 4 PCB with all of those bugs fixed.