IBM's mainframes were in a weird place in the 1990s, because they had a 31-bit virtual address space, i.e. 2 GiB, but the physical machines could be equipped wi

IBM's mainframes were in a weird place in the 1990s, because they had a 31-bit virtual address space, i.e. 2 GiB, but the physical machines could be equipped with a lot more RAM. One way to utilize this surplus memory was to use it as a RAM-disk and turn it into a swap device. It was stop gap measure before their CPUs went 64-bit, but at the time it was kind of a clever solution.