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Why we don't have 128-bit CPUs
(www.xda-developers.com)
This is a most excellent place for technology news and articles.
We do, depending on how you count it.
There's two major widths in a processor. The data register width and the address bus width, but even that is not the whole story. If you go back to a processor like the 68000, the classic 16-bit processor, it has:
Some people called it a 16/32 bit processor, but really it was the 16-bit ALU that classified it as 16-bits.
If you look at a Zen 4 core it has:
So, what do you want to call this processor?
64-bit (integer width), 128-bit (physical data bus width), 256-bit (widest ALU) or 512-bit (widest register width)? Do you want to multiply those numbers up by the number of ALUs in a core? ...by the number of cores on a piece of silicon?
Me, I'd say Zen4 was a 256-bit core, but you could argue any of the above numbers.
Basically, it's a measurement that lost all meaning so people stopped using it.
I'm surprised some marketing genius at the intel/amd hasnt started using the bigger numbers
I expect the engineers are telling the marketing people "No! You can't do that. You'll scare everyone that it's incompatible."
32bits is compatible with 64bits, why wouldn't 128 bits be too?
64bit cut out 16bit compatibility. So I'm guessing the fear is that 128 would cut 32.