Well, we're talking three things: processor architectures, processors, and systems. The 21064 is definitely on-topic, as are the early AXP systems (DEC 3000/4000/7000) The basic Alpha architecture is probably irrelevant, because I have never heard a discussion about architectures as being on or off topic, generally discussions of that nature are sufficiently technical to pass. The R4000 is an interesting case, because the chip predates the 21064, but (a) early versions could not run 64-bit since they had a bug in the MIPS-III instructions and (b) no R4000/R4400 systems were 64-bit capable until the Onyx in 1993 unless I've missed something. In short, therefore, the 64-bit potential of the R4000 arrived first, but 21064 realized a 64-bit system first. Take that how you will.