In a previous life at a bank, I had the joy of working with a real S390 system. Absolutely solid as a rock; but that perhaps was also a reflection of the quality of the software on it, written with very well known user requirements and acknowledging of the limitations of the communications systems of the time.
I also keep a model around written originally for S390. Former administrators of the model decided that rather than migrating the Fortran to a modern architecture, that they would instead run it in one of those (rare) commercial emulators... for DOS.
How many layers of emulation do you want?!? S390 in DOS in VirtualBox (or other VM of choice). It works well in Dosbox though of course such use is definitely against the legal boilerplate of Dosbox.
Biting the hand that feeds IT
