Moore said: "GreenArrays' computers have a unique mechanism for implementing stacks with hardware: a stack is a set of registers with a pointer to the one currently on top. The pointer is moved up or down as required. The data is not moved, merely a pointer to the register in which the data is stored. This saves energy. "

Unique? I've been doing ASIC design for more than 20 years and that is how it has always been done.