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Are there any reasonably fast emulator for the system 360? It seems like ridding yourself of vendor lock would be goal one. Then add an interface wrapper that

Are there any reasonably fast emulator for the system 360? It seems like ridding yourself of vendor lock would be goal one. Then add an interface wrapper that logs inputs and outputs for several years to build validation tests for any ports or upgrades. It seems like a truly insane effort to port 20e6 lines of assembly and expect to get identical behavior. I doubt the current behavior is even fully documented. Ensuring identical outputs for a lot of recorded data seems at least slightly more valid than trying to go back to documentation or requirements. Perhaps the simplest way to migrate the IRS code is to make the laws simple enough you don't need 20e6 lines of assembly to implement it anymore?

pdntspa 4y ago
Provided the 360 CPU is well-enough documented, I don't see the problem here?
agentbellnorm 4y ago
With enough saved input/output data, maybe some parts could even be replaced by a ml model? Not 100% serious but then again seems like serious resources are put into this problem, so maybe worth a try
- kadoban 4y ago
  An AI-aided translation might make more sense, since at least you could review that for correctness and it'd likely be easier+cheaper to run the result.
  - jmartrican 4y ago
    I wonder if an AI system for the IRS would use double float or big decimal types to do its math.
hinoki 4y ago
System 360 is very well documented by the Principles Of Operation: https://dl.acm.org/doi/pdf/10.5555/1102026 https://dl.acm.org/doi/pdf/10.5555/1102026 So much better written than Intel’s Software Developer Manuals, where anything complicated is just “look at these three pages of c-like pseudo code we probably pulled from our tests, good luck!” IBM themselves have had to maintain backwards compatibility for > 50 years, and there is a long history of compatible machines: https://www.computerhistory.org/revolution/mainframe-computers/7/169 https://www.computerhistory.org/revolution/mainframe-compute... So all the strange behaviours are well documented.
kens 4y ago
If you're looking for an open-source 360/370/390 emulator, Hercules is probably what you want: http://www.hercules-390.org/ http://www.hercules-390.org/

pdntspa 4y ago

Provided the 360 CPU is well-enough documented, I don't see the problem here?

agentbellnorm 4y ago

With enough saved input/output data, maybe some parts could even be replaced by a ml model? Not 100% serious but then again seems like serious resources are put into this problem, so maybe worth a try

kadoban 4y ago
An AI-aided translation might make more sense, since at least you could review that for correctness and it'd likely be easier+cheaper to run the result.
- jmartrican 4y ago
  I wonder if an AI system for the IRS would use double float or big decimal types to do its math.

hinoki 4y ago

System 360 is very well documented by the Principles Of Operation: https://dl.acm.org/doi/pdf/10.5555/1102026 https://dl.acm.org/doi/pdf/10.5555/1102026 So much better written than Intel’s Software Developer Manuals, where anything complicated is just “look at these three pages of c-like pseudo code we probably pulled from our tests, good luck!” IBM themselves have had to maintain backwards compatibility for > 50 years, and there is a long history of compatible machines: https://www.computerhistory.org/revolution/mainframe-computers/7/169 https://www.computerhistory.org/revolution/mainframe-compute... So all the strange behaviours are well documented.

kens 4y ago

If you're looking for an open-source 360/370/390 emulator, Hercules is probably what you want: http://www.hercules-390.org/ http://www.hercules-390.org/