[junon]

> input spans more than half of the virtual address space

Not only that, but in practice most general purpose operating systems are designed with higher-half kernels[0].

[0] https://wiki.osdev.org/Higher_Half_Kernel

[valleyer]

32-bit Mac OS X was not (it had a 4/4 scheme).

Though even then I'm not sure you could reliably allocate two gigs of contiguous virtual space without running into some immovable OS-provided thing.