And on the PDP-10, it contains a virtual robot to toggle the virtual switches on the virtual PDP-11, to load a loader that runs the virtual tape drive to load the startup program for the PDP-10.

j/k I have no idea how linux boots on Z.

This actually isn't too far from the truth. The VAX 8800 series of minicomputers used a cut-down PDP-11 to boot it, and to act as a console.

https://en.wikipedia.org/wiki/VAX_8000#VAX_Console

Fun to think that it’s more or less how zVM starts stuff. It took me a while to mentally accept the concept of VM that zVM (in reality, I was playing with VM/370) has, which is not like anything non-mainframe users would be familiar with.

But you can also run Linux directly on an LPAR under the thin hypervisor (which I forgot the name) that runs zVM.

The indignity of the mainframe is that it’s booted under control of an x86 machine that itself boots up as an 8086. At least these days the service elements run Linux.

> But you can also run Linux directly on an LPAR under the thin hypervisor (which I forgot the name) that runs zVM.

The name is PR/SM - which, from what I’ve heard, actually started life as a modified version of VM

> The indignity of the mainframe is that it’s booted under control of an x86 machine that itself boots up as an 8086. At least these days the service elements run Linux.

Poor OS/2, no more booting mainframes for it anymore, unless they are very old ones

> Poor OS/2, no more booting mainframes for it anymore, unless they are very old ones

At least it's not Windows.