[SIGCIS-Members] Longest lived computer architecture: System/360?

thomas.haigh at gmail.com thomas.haigh at gmail.com
Thu Oct 8 10:00:26 PDT 2020

Another candidate record I was thinking about was the longest lived computer
architecture. Longest lived here being the uninterrupted production and sale
of machines. (So retro revivals don't count). Architecture being able to run
object code without recompilation, and without emulation.


I'm assuming that would be the IBM System/360, with the /370, /380 etc.
being considered extensions of the same architecture.  It is widely claimed
(e.g. by Wikipedia) that even the current IBM Z family of mainframes has
retained compatibility with the System/360
(https://en.wikipedia.org/wiki/IBM_Z) such that "Many applications written
for these systems can still run unmodified on the newest IBM Z system over
five decades later." Although as virtualization is so central to mainframe
architecture form the 1970s onward I don't have a clear sense of how much of
this is straightforward hardware compatibility and how much is provided by
the virtualization software.


If we accept this as an uninterrupted architecture, then that give 1964 to
2020, or 56 years and counting. That appears to be longer than the Intel
8086, which has been incrementally extended to the present day, with the x64
architecture, and was launched in 1978, making it 42 years old. 


I know that some of the first System/360 models included emulation of even
earlier machines, and that the original 8086 was designed with early
conversion from earlier Intel chips in mind. But in both cases they seem
distinct enough to set a new standard.


An I missing any other contenders? Or does anyone know enough to make a case
that, contrary to popular belief, true System/360 hardware compatibility was
lost at some point?





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