2.4. Migration to 64-Bit Architectures
A strategy for retaining the existing customer base typically accompanies any major change of architecture in the computer industry. IBM had that concern when two not-so-similar lines, System/36™ and System/38™, were going to be supplanted by the AS/400® line. A combination of hardware and software emulation strategies made that transition rather successful.
When Digital Equipment Corporation introduced the 32-bit VAX line, the first few implementations contained hardware emulation of the instruction set of the 16-bit PDP-11 line. Later VAX implementations omitted those hardware features, substituting PDP-11 software emulation.
A mixed approach was taken toward assistance for the existing customer base with ...
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