>> A2

> I hadn't heard of that one

Product-wise, it's only ever been used in the BQC (Blue Gene/Q Compute) chip. As has been revealed when the core was open sourced, the PowerEN chip mentioned in the Wikipedia article was never released.

> PowerISA v2.06 […] to the best of my knowledge doesn't allow 64-bit processors
> to not implement a 32 bit mode. After checking out the linked A2 documentation,
> it does imply that the 32 bit mode is also available on those CPUs.

I don't remember where exactly I got this (mis)information from, but know I read it somewhere in 2010 when the A2 was announced and unfortunately didn't bother to check even after a link to the user manual was added to the Wikipedia article in 2013. Shame on me. Thanks for taking the time to verify and correct my misconception :-)