[dfox]

The 128bit pointer intermediate code is used on what IBM calls "midrange systems" (ie. AS/400), not mainframes. IBM mainframes execute their machine code directly and the ISA is designed such that it allows for efficient virtualization since beginning and is extensible and backwards-compatible. Otherwise the IBM mainframe magic is in IO offload and truly immense memory bandwidth. On the other hand, Unisys systems use architecture that is significantly different from what today's programmer would expect, with completely different memory model originally implemented in hardware (which essentially combines the memory protection model implemented on AS/400 in software with lisp machine-style pointer tagging).