Only one case so far? Apple has taken the Mac from Motorola 68000-series chips to PowerPC to Intel x86 and now to the ARM-based M1. That’s 4 different architecture in less than 4 decades.
I also said 'architecture change' so by your count that would be 2. But Rosetta was only for PowerPC to x86 wasn't it? There seems to have been emulation for the 68x chips but was it seamless without breaking anything?
I mean any company could change architecture but rely on a customer using an emulator that isn't really not breaking things.
So by my count, 1, but if I am wrong and the 68x translation was equally as seamless and breakless than 2.
But to say it was unheard of you need to reference all the other companies that transitioned architecture and broke stuff. I can't think of another general computing supplier who did that but I might be wrong - can you give an example?