FCE Ultra DC
Takayama Fumihiko the author of the 'unofficial' NesterDC, NesterDC expanded, and the later official versions of NesterDC began porting FCE Ultra (another NES emulator) to the Dreamcast sometime in 2001. He stated originally that the APU engine of FCE Ultra was too heavy for the Dreamcast, and was in the process of developing his own.
In the end all that was ever released was the source code, which was claimed to have been close to the speed of the then current NesterDC.
Unfortunately, that source code has been lost to the defunct internet pages of the past, and has never been recovered.
Below is the original post from Takayama's archived site:
"2001/11/04 00:51 (JST)
- fceu-0.1.tar.gz (553KB, source code only)
This is FCE Ultra port to Dreamcast. It's too primary stage, but the speed is equal or upper than NesterDC. (And it's code written by C. It's very handy). We'll feedback experience of FCE Ultra porting to NesterDC.
Original FCE Ultra APU engine is too heavy for Dreamcast, so we must develop APU engine for FCE Ultra. But I cannot touch this code now because I'm in release engineering for NesterDC-4release. Would you write code?
It's build process is same as NesterDC, and it has same develop environment."