OS/400 doesn't run on s390/zenterprise. It runs on pSeries (POWER8), which also run AIX and Linux. OS/400/IBM i (or whatever its called this week) is actually

OS/400 doesn't run on s390/zenterprise. It runs on pSeries (POWER8), which also run AIX and Linux. OS/400/IBM i (or whatever its called this week) is actually probably one of the cooler OS's still around. It should be mandatory study in any comp sci/comp eng OS classes, but sadly its not and because of that, a lot of wheels are being reinvented.