SmallPCFX is a PC-FX emulator based on a stripped down version of Mednafen. The current aim is to have a decently fast PC-FX emulator for platforms like the GCW Zero and the RS-97.
Currently though, while it runs faster than stock Mednafen, it's still not fast enough. This needs some frameskip before it might be playable (to some extent) on low-end hardware.
Like Mednafen, a bios/firmware is required. Put it in .mednafen/ (Should be found in your HOME directory or /mnt/int_sd/.mednafen for the RS-97) and rename it to pcfx.rom. A bad dump of the BIOS is floating around and won't work with Mednafen or this emulator, here's the MD5 hash of the working one : 08e36edbea28a017f79f8d4f7ff9b6d7
Exit is mapped to SDLK_END, which is the power button on the RS-97.