> Why cannot the mainframes be replaced with virtual machines and the target binaries replaced with the identical output from a language with more than one comp

> Why cannot the mainframes be replaced with virtual machines and the target binaries replaced with the identical output from a language with more than one compilation target? It seems from the outset this is entirely possible and practical given how much more compute is available from modern architectures. Because mainframes are more than just a quantity of computation. Their hardware and software has prioritized reliability and resiliency far more than the PC architecture, which pretty much everything else is based on nowadays (and which started out and remains mainly about low-cost). In some ways the approach you describe would be like replacing a ZFS RAID array with an a single large disk with a FAT filesystem. It's possible, but you probably don't want to. Full disclosure: I'm not a mainframe developer, but I've read quite a bit about them.