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clownmdemu – frontend v0.2 & libretro v0.1

It’s been too long, but finally my emulator has an update!

Since the first release, the emulator has been greatly optimised, some inaccuracies in the 68000 interpreter have been addressed, and the occasional missing CPU instruction has been added. Compatibility with games should be a bit better than before, but still not great as many essential features of the Mega Drive are not emulated.

The standalone frontend has had some extra debug menus added, which allow you to view the registers of the YM2612, 68000, and Z80:

New to the emulator is a libretro core frontend, allowing the emulator to be used by libretro implementations such as RetroArch. It lacks the debug menus of the standalone frontend, but makes up for it with features that libretro cores get for free, like customisable controllers and shaders:

In theory, the libretro core should provide a simple way of getting this emulator running on a variety of platforms: just compile the core into a library (static or shared), and use it in tandem with a libretro frontend such as RetroArch.

During the development of this update, I have set up a test suite for the 68000 interpreter which allows me to check that each instruction does as it is supposed to. It was this test suite that notified me of how the word-size ADDA, SUBA, and CMPA instructions were pitifully broken. I’m surprised that this didn’t break Sonic 1, 2, or 3&K, but it did break Linux.

Yes, Linux: to test my 68000 interpreter, I extracted it from this emulator and used it to create an emulator for the 68 Katy, a hand-built computer that runs Linux. You can read more about it here.

I also made a small benchmarking tool which measures the speed of the core emulation logic. This is useful for measuring the impact of optimisations and the difference in speed between platforms.

Overall, this has been a rather incremental update. Rather than being focussed on optimisation and refactoring, I hope that the next update will be focussed on improving compatibility and emulating more features of the Mega Drive.

You can find the standalone frontend here, and the libretro frontend here.


One thought on “clownmdemu – frontend v0.2 & libretro v0.1

  1. Don’t get me wrong, it’s a good work here, I like the debuggers and there’s potential. But some quick testing revealed it lacks the Window plane!


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