On Sat, Jan 30, 2016 at 12:42:59PM +1000, Warren Toomey wrote: > Naoki, I am trying to build these systems following your instructions. > I am using SimH 3.8.1 on a 64-bit Ubuntu system. I am seeing these problems: Jason Stevens pointed out the problem. SimH needs to be compiled with -O1 to get it to work on 64-bit Ubuntu systems. Thanks Jason, Warren