I work with IBM i/AS400 servers and those are not exactly the quickest thing to "reboot" (technically an IPL). Especially the old ones. I have access to the HMC/console but even this sometimes takes several minutes (if not dozens) just to show what's going on.

It's always a bit stressful to see the codes passing one after the other and then it stops on one and seems to get stuck there for a while before continuing the IPL process. Maybe it's applying PTFs (updates) or something, and you just have to wait while even the console is blank.

I've been monitoring those servers for years and I'm still sometimes wondering if it hanged during the IPL or if it's just doing its thing, because this part, even with codes, is not very verbose.

Fortunately it's also very stable so it pretty much always comes back a few minutes after you start wondering why the hell it's taking so long.