Updated 10/01/21

This guide is dated to the pre-Apple Silicon / Big Sur era. For users on macOS 11.x Big Sur and above (Apple Silicon and Intel) see the new updated guide: Mac MAME Arcade emulation & NeoGeo using OpenEMU and SDLMame for Apple Silicon or Intel.

OpenEmu also sports MAME Arcade emulation support, but its a bit tucked away.

Step 1: Download OpenEmu Experimental

Go to openemu.org and click the swatch and download OpenEmu Experimental, and install it.

website of OpenEmu

This scfeenshot of the OpenEMU site is old. The design on the OpenEMU website has slightly modified to make the experimental version easier to find

Step 2: Install the MAME core

Once installed, launch OpenEmu, open preferences, and select cores. Click the install button next to MAME.

OpenEmu cores preferences

Step 3: Install games

Games can be nabbed from the usual suspects like emuparadise (defunct), the legality of this is fairly grey. OpenEmu only supports zipped ROMs, so if the ROM comes in a .gz or .rar, be sure to decompress its contents and rezip it. Name it the exact name as before (but with the new extension of zip). OpenEmu's MAME core is version 0.149.1, so its significantly behind the windows version (from 2013 to be exact). Some sites will list the earliest known support needed for the rom in question.

OpenEmu with NBA Hangtime (arcade)

Notably, you'll want access to the dipswitches, hitting F2 repeatedly while the game is launching will take you to most ROM bios screens that enable modes like free play. Note, I had issues resuming games and had to force quit MAME resuming so you may want to hold off resuming games.

OpenEmu with NBA Hangtime (arcade) dipswitches

Optional: NeoGeo Emulation

Emulating NeoGeo games requires one extra step, you'll need to get the NeoGeo ROM, the one I used is from emuparadise which is now defunct, try a popular search engine and search "Neo Geo BIOS". Drag the Neo Geo zip into OpenEmu. You'll see the NeoGeo ROM in your game list, but ignore it and double-click the games as you normally would.

Good luck with OpenEmu. I suggest checking out the Dolphin Emulator as it has a great macOS port for GameCube and Wii, and PCSX2 for Windows for Playstation 2 emulation. Both are able to play old games in HD and UHD depending on your CPU/GPU.

Other recommendations from this blog:

Updates: 4/21/20 - copy editing, note about layout change on OpenEMU's website, striking out emuparadise as its now defunct.