Caprice32 is one of the best emulator of the Amstrad CPC home computer series running on Windows and Unix, written by Ulrich Doewich. This emulator faithfully imitates the CPC464, CPC664, and CPC6128 models (see Caprice32 project).
Here is a port on GP2X of the version 4.2.0 that ZX-81 had previously ported to PSP.