You're right, you have to unplug one of the boards while you program the other board, and it works. I was just thinking for the longest time theres no way they didn't build something into the software to toggle between multiple boards. I assumed you could use an iPac4 and an iPac2 together but theres nothing on the Ultimarc website that says they have that capability. They only talk about the UIO having this capability. So confusing. Ultimarc would save us and them a bunch of headaches if the would just create normal documentation like every other software/hardware company. How hard could it be? Their stuff isn't that complicated, but we have to jump through a bunch of hoops to figure out simple things that could just put in the help file.