All emulators can potentially run slowly if you have not configured them correctly. I run Snes TYL 0.3 ME on my 1.5 Psp and it is very fast, very near full speed for most games and all other games that I enjoy are playable. That particular Snes emulator was updated only a few weeks ago.
Also the GBC emulator is one of the best and very worth trying out, it is called Rin V1.32 or you can also use Homers Rin but that is optimised for 2.01+ firmware.
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