> Unfortunately, it ended up at HP in the Itanium era, where it seems to have died off.

My dad continues to maintain NonStop systems under the umbrella of DXC. (Which is a spinoff of HP? Or something? Idk the details.) He worked at Tandem back in the day, and has stayed with it ever since. I think he'd love to retire, but he never ends up as part of the layoffs that get sweet severance packages, because he's literally irreplaceable.

The whole stack got moved to run on top of Linux, IIRC, with all these features being emulated. It still exists though, for the handful of customers that use it.