IBM released their A2I and A2O cores https://en.wikipedia.org/wiki/IBM_A2 https://en.wikipedia.org/wiki/IBM_A2 open source https://github.com/openpower-cores/ h

IBM released their A2I and A2O cores https://en.wikipedia.org/wiki/IBM_A2 https://en.wikipedia.org/wiki/IBM_A2 open source https://github.com/openpower-cores/ https://github.com/openpower-cores/ The A2I was used in the Blue Gene/Q supercomputer line. A2O is out of order variant which was not used in a product. They have multi-threading, hypervisor features, superscalar, etc. They are "real" cores, not state of the art but probably not too far off. Not likely to be something you can easily just pick up and learn without good HDL knowledge and working understanding of processor implementations though.