If I remember correctly, Gordon Bell said roughly that you could update an architecture once, but after that things get to be a mess. You might want to read "The Soul of a New Machine" for an interesting story. It was about Data General's attempt to build a 32 bit computer. This would have been the 3rd generation, after the Nova and Eclipse
On 05/22/2016 12:11 AM, D. Hugh Redelmeier wrote: lines. I read this book back in the days when I was maintaining Nova and Eclipse computers, so I had a bit more insight than most.
One of Intel's motivations for Itanium seemed to be to own the architecture. It really was unhappy with having given a processor license to AMD.
One problem with that is some customers, particularly military, were allergic to single source equipment. As I recall, Intel had to second source their products because of this. As a result, AMD, Siemens & NEC, IIRC, all made compatible "Intel" products under licence.