Per system. Check manual/QVL of ANY 55x0 chipset board.
Note that boards with 12 slots might actually work with 48GB of non-ECC RAM, but you will not find it on any QVL. And possibly the BIOS might intentionally not allow it.

Quote Originally Posted by mattkosem View Post
24GB per IMC or per system? Any docmentation to support that?

--Matt