I am glad this is still going - if only for the reason that different computer architectures fascinate me. IIRC they said the belt machine thing maps well to SSA - you specify your operands by position, but the destination register is implicitly the back of the queue - in kind of the same way that each "a op b" in SSA is saved to a new variable.
Ivan is a compiler guy, and I've always seen a huge impact of "compiler guy" thinking on Mill -- in a much smarter way than how "compiler guy" thinking sank Itanium.
http://millcomputing.com/wiki/Belt