OpenEmu 2.0 introduced 16 new cores along with hundreds of bug fixes and lesser features. OpenEmu 2.0 began requiring a minimum of OS X El Capitan 10.11, dropping support for Mac OS X Lion (10.7.x) through OS X Yosemite (10.10.x). Introduced on Wednesday, Dec 23, 2015, (exactly two years after 1.0) OpenEmu 2.0 was released. A Wednesday, Octo(296 days later) midstream update to the OpenEmu library (1.0.4) would introduce Stella, a core emulating the 2600, a 2nd generation console from Atari. OpenEmu 1.0 needed Mac OS X Lion (10.7.x) to run. OpenEmu 1.0 released on Monday, Decemwith 12 'cores' emulating Nintendo, Sega, NEC, and SNK's home, tabletop, and handheld consoles from the 3rd through 7th video game console generations. Weinberg and his friend, Ben Devacel, began searching for more developers to port other emulators to macOS, which led to the name change to OpenEmu in 2009, to better describe the multi-system emulator.

OpenEmu was first released on Wednesday, July 4th, 2007 as OpenNestopia, a Cocoa-port written by Josh Weinberg for then Mac OS X 10.4 Tiger of the NES/ Famicom emulator Nestopia (written by Martin Freij).

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