[trollbridge]

IBM mainframes can run software written in the 1960s without modification. There’s no reason anyone would keep using an obsolete mainframe, and IBM usually leased them anyway and would refuse to support obsoleted machines.

[PaulRobinson]

You clearly don’t know what has been happening in the World of S/360 (and similar), support contracts in recent years.

Costs are rising heavily. IBM sold off most of that business, to people who don’t really want it as the skill base to support it is retiring and it’s too expensive to easily replace. This has been going on for a couple of decades, but it’s now gaining more and more pace.