Exotic architectures the standards committees care about

I know that the C and C++ standards leave many aspects of the language implementation-defined just because if there was an architecture with other characteristics, a standard confirming compiler for that architecture would need to emulate those parts of the language, resulting in inefficient machine code. Surely, 40 years ago every computer had its own unique specification. However, I don't know of any architectures used today where: - `CHAR_BIT != 8` - `signed` is not two's complement (I heard Java had problems with this one). - Floating point is not IEEE 754 compliant (Edit: I meant "not in IEEE 754 binary encoding"). The reason I'm asking is that I often explain to people that it's good that C++ doesn't mandate any other low-level aspects like fixed sized types†. It's good because unlike 'other languages' it makes your code portable when used correctly (Edit: because it can be ported to more architectures without requiring emulation of low-level aspects of the machine, like e.g. two's complement arithmetic on sign+magnitude architecture). But I feel bad that I cannot point to any specific architecture myself. So the question is: what architectures exhibit the above properties? † `uint*_t`s are optional.