Intel tried twice to replace the X86 architecture.but IMHO, their excessive reliance on the X86 architecture blindsided them on the ARM and GPU revolution.
The I432 used a “capability” architecture, in which each process needed a token for any data segment it could access. This provided bullet proof (relatively) security. The problem was that a procedure call, on a 5MHz processor, took milliseconds. The overall performance was 1/4 of the x86 which cost far less.
Then there was the Itanium, jointly developed with Hewlett Packward [sic]. It used a unique idea that the hardware would not execute instructions in parallel unless designated in instruction, leaving such decisions to the compiler. The designers claimed they could get over 4 instructions per clock, compared to 2.1 with the existing X86. When it was built, the real number was, wait for it, 2.1
In both cases, these processors were designed by academics with no real world credentials. IMHO that is why both failed.
I was at Intel at the time of the Itanium release, working on the X86 side, so maybe I am a bit biased. And guess what? The group I worked for had designed an enhanced ARM architecture processor that was, at 1Gz, the fastest made. Intel never released it. This was in 2002.




