[tony duell] :But there's very few similarities between (say) the PDP8, :the PDP10 and the PDP11. having read up on these, we'd beg to differ here. it seems to us that all the pdps followed a very definite architectural pattern, with the exception of the pdp11 which struck us as a major departure (the dg nova has more in common with the early pdps than the pdp11, to our mind). ok, so they weren't anything like binary compatible (well, between families - there was the 5,8,12; the 1; the 4,7,9; the 6,10; and then the nova / eclipse. all were basically accumulator-plus-memory architectures, it seems, even the 6 and 10; all had simple, regular, but very powerful instruction sets with minimal formatting and all instructions in one word (if you view the 6 word size as 18 bits and call it a double word machine :> ) - we can discern a very distinct family resemblance on the way up. the pdp11 marked a major change, from a 1-address to a 2-address architecture. we aren't sure it was a good thing... anyway, the pdp8 is much more similar to the 10 than either is to the 11. -- Communa (together) we remember... we'll see you falling you know soft spoken changes nothing to sing within her... Net-Tamer V 1.08X - Test Drive