>I never mentioned Windows but it's ridiculous to imply its backwards compatability is all on Microsoft.

I never said that. Windows was just an easy example.

>Show me a single example of a backwards breaking change in x86 that Windows has to compensate for to maintain backwards compatability.

- The shift from 16-bit to 32-bit protected mode with the Intel 80386 processor that fundamentally altered how the processor managed memory.

- Intel 80286 introduced a 24-bit address bus to support more memory, but this broke the address wraparound behavior of the 8086.

- The shift to x86-64 that Microsoft had to compensate with emulation and WOW64

Any many more. That you think otherwise just shows all the effort that has been done.