From Apple POWERPC days and Itanium, wasn't x86 supposed to run out of steam, it has inherited so much legacy cruft that a clean room implementation supposed to be faster?
That was what I heard as well, it didnt (obviously) happen in reality, I suspect that a large reason was simply the power of the x86 market, creating an entirely new market is very expensive, I believe the number that was being toutede 10 years ago was something like 2 billion USD from Intel, and an unknown number from HP.
Now when you look at the revenue made on the sales of this new product it does not look good, have a look at what AMD did by adding the 64-bit support to the x86 architecture, did they spend 2 billion.? who knows, what I do know is that the sold vastly more chips and morer importantly a much greater revenue.
I personally believe that Itanium was doomed from the outset because it had to emulate x86. Why did they not integrate an x86 component to avoid emulation.? Why did they not make it 128-bit from the outset, 64-bit was merely to compete with existing technology, rather that surpassing it. It was doomed from the manufacturing point when best part of a decade ago they had made a 1-billion transistor Itanium - it was not a great architecture either, and again I am not sad to see it going away, and neither are Intel.
As far as POWERPC for the MAC is concerned, the same points apply, its not x86, the revenues were not there to fund investment, they were for x86 so POWERPC has bitten the dust - however they were essentially on a knife edge for years because I cant even name another user of POWERPC chips other than Apple.
Wasn't Dec Alpha an example of what could be done with RISC?
DEC were destroyed by arseholes (HP i think it was), they had some of the best ideas, performance, and were going places even with minimal investment, but they were sadly destroyed.
Regarding RISC, remember that part of the core of AMD processors some years ago was (is.?) based on a RISC architechture that they licences from Alpha, along with a BUS architechture that they stopped using when they had developed HyperTransport.
The interesting thing of the future is ARM and GPGPU, along with of course how much more that can be squeezed out of x86, 128-bit perhaps, AMD is already there (Bulldozer) with a a 128-bit Floating Point unit.