The IBM mainframe: How it runs and why it survives
The reason mainframe persists is it's a pretty slick development and deployment environment. A lot things you might cobble together as dependencies - like maybe a database or a message queue, or observability facilities or even deployment strategies like hot-hot deployments - they're all just built in to the platform. That means they're trivial to consume and they're fully supported by one vendor. It's like the worlds most comprehensive application development framework.Going back to the hardware that everyone likes to focus on, it's less radically different from normal servers today than it was historically. The mainframe today is a 19 inch rack like any other. By that i mean it is not only a 19 inch rack like your x64/ARM servers are but also the same power density (32 or 64 amp racks), cooling requirements etc.The most interesting bit is the software, not the hardware. There are cool hardware aspects too - but focus on them and you miss the real reason these things are popular in certain environments.