Ijor released the source code for FX68K a cycle-accurate Motorola 68000 soft-core (soft cores are components, rather than whole platforms) that was first hinted at in the release of his Atari ST core FXCAST. The 68000 was a common processor used in a wide range of consoles, home PCs, and arcade games. Having a perfect version of it means that several cores will essentially get an engine swap under the hood (Genesis, x68000, Amiga, etc). And it will make the development of other 68K-based platforms that much easier to implement (Neo Geo, Saturn, Jaguar, etc).
FX68K Source (Verilog)
When ijor first mentioned the accuracy of his 68000, I posted a video explaining why it is such a huge development for MiSTer: