The IBM i (formerly AS/400) platform, despite its popularity over several decades as a server for business applications—and its importance in computing history

The IBM i (formerly AS/400) platform, despite its popularity over several decades as a server for business applications—and its importance in computing history as an example of features such as object-oriented, single-level storage—doesn’t have a comprehensive, generally-available emulator, as far as I know. For anyone outside IBM, developing one might be difficult: neither the original, low-level CISC instruction set used through the 1990s, nor the PowerPC AS extension to the POWER architecture that replaced it, has been fully described in public documentation.