Since additional context was requested in the realted OS 2200 thread:
OS 2200 is the operating system for the ClearPath Dorado mainframe systems. The OS 2200 operating system is directly descended from EXEC-8 and the Unisys ClearPath mainframes in this series are the descents of the UNIVAC. See https://en.wikipedia.org/wiki/OS_2200 for info.
MCP is the operating system for the ClearPath Forward mainframe systems. The MCP operating system is directly descended from the original MCP and the Unisys ClearPath mainframes in that series are descendants of Burroughs Large system mainframes. https://en.wikipedia.org/wiki/Burroughs_MCP for info.
These are essentially the only two widely deployed mainframe systems that remain in constant mission-critical production outside of IBM systems and I think it is quite the treat that Unisys, the current owner of these platforms, has made free-of-cost virtualization solutions for these platforms available to mere hobbyists and enthusiasts.
Far as widely deployed, Group Bull w/ GCOS seems to be making plenty of money. I’d guess Fujitsu’s are doing OK, too, which what they’re putting into the SPARC chips.
I admit totally forgot about GCOS systems, likely because I’ve never encountered one in real life, so out of sight out of mind, I guess. A quick bit of research confirms the Fujitsu mainframes are indeed very popular in Japan and Asia, which isn’t a small market.
I wonder how the the number of Bull and Fujitsu installations compare to Unisys? I’d still bet for sure IBM makes them all seem insignificant! Come to think of it, Stratus systems essentially have a monopoly in their niche markets and absolutely aren’t going anywhere anytime soon and NonStop systems are widely deployed in extremely critical environments as well.
IBM has about 85-90% with others splitting the rest. NonStop certainly kicks ass with VMS clusters nearly as reliable used by some instead. HP’s temporary suspension of VMS probably solidified NonStop as best choice. Don’t forget Stratus, though, as they got some big deployments like in airlines. They’re cheaper than NonStop so naturally get many of the same kinds of customers. Especially for databases.
One thing I had in mind was to do a NonStop-like solution with high-end, embedded boards that supported lockstep. Could probably emulate something like Cyclones or pairs of pairs model pretty cheap. Then, make the software a cluster style to scale out instead of up. I obviously lack the capital but like doing those designs on paper. :)
Stratus is ubiquitous is banking and big finance in certain critical roles as well.