> Maybe it's designed to be compatible.

Okay, that would be what I told I suspected regarding supervisor mode compatibility.

> OTOH it could just be marketing.

I doubt that, else debugging tools developers Abatron and Lauterbach wouldn't list it under PPC4xx I think.

> AMCC have the 460 label on different chips with 440 cores
> and others with 460 cores...

I'm aware of that. But still, subsuming any core/chip under 'PPC4xx' is yet another quality than just calling a PPC440 core based chip a 'PPC460'.

> Certainly $5.6 million isn't nearly enough to design a core.

So I guess 5.4 million wouldn't suffice all the more ;-) Thanks for the insight as I'm really not aware of how much money is usually involved in such undertakings.