Textmode Virtual Macaroni, or TMVM, is a simple poorly-designed (yes, that's a feature) simulation of a register-based system.It currently has an addressable memory space of 256 segments containing 256 bytes (00..ff) each, for a total of 65536 bytes (64KiB), and runs at a nominal speed of 1MHz.
It's not presently useful for much of anything, it is also likely to be unstable and unreliable, so have fun! :D
In all honesty, TMVM could be used as a toy system, or as an instructive aid (once it's more stable). It's nigh-complete lack of higher-level features or space means it's effectively a void, an empty sandpit, in which you can do pretty much anything you want without stepping on anything's toes.