For 32-bit PowerPC, PowerOpen is the ABI used in PPC Mac OS and OS X (largely, with a couple minor differences) and AIX. The System V ABI is pretty much everything else, but it's really a misnomer since the *BSDs on 32-bit PowerPC use SysV too.

PowerOpen is still a thing for 64-bit, see https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-...

As memory serves me, on 32-bit you would pass a 64-bit value in adjacent 32-bit registers in big-endian fashion.