I have been running a full IBM System/370 Mainframe on a $20 Raspberry Pi Zero for ~5 months. Thousands of lines of COBOL and HLASM running flawless. Tested an entire bank’s mainframe COBOL on it.
They state on a Raspberry Pi Zero it is rather slow but it’s possible to run it on a faster Pi or another Linux system. The software is possible due to tk4- and KICKS for TSO. It even runs Colossal Cave:
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