TTL homebrew CPUs

Stroller wrote: Agreed. I even went looking for neons at Bletchley yesterday, but what I remembered as being boxes of them turned out to be ordinary panel lamps :-( Farnell look to sell some cheap ones though, so I might do some experimenting. I've got some Nixies gathering dust - I wanted to use them for something that wasn't a clock, but this neon one is sufficiently oddball that I'm very tempted... I'm still not up to speed with the theory, though - I can see how the ring counter operates once one tube is lit, but I'm not quite sure how the power-up initial status with only the first tube in each counter lit is arrived at... (i.e. how is it guaranteed that only one tube fires, rather than none or several? Is one tube chosen to have slightly different characteristics to the rest in the ring or something?)