Hi there, Perhaps someone who is a little more familiar with the innards of the PDP8/Ses can answer this... Are the individual flip-flops arranged like a shift register or a set of latches? In other words, when data is being clocked into a register, does a bit get put into (say) AC0 then bumped along until it eventually ends up in AC11, or are all the D lines of the flip-flops connected together, with each one being clocked in turn? Gordon.