After Picodrive, here is PCSX_rearmed for Leste on N900.

https://github.com/Arno1103/pcsx_rearmed_leste

It works full speed using GPU_UNAI, CPU clock set at 57% and Dynarec recompiler.
(note: PS1 full speed is around 25 fps with PAL and around 30 fps with NTSC games)

Similar key mapping hardcoded modifications to Picodrive has been done with pcsx to be able to navigate in the menu and select the right GPU plugin and other essential things.

To run it easely, just clone the repo in the directory of your choice:

With a good uSDcard it takes around 15 min to compile.

Then as usual with psx emulators, the configuration is a bit tricky:

Create a /bios directory in your pcsx folder and add scph1001.bin bios file.

Create a /.pcsx directory (in your pcsx folder) and create a pcsx.cfg file inside with read-write access.

Now you are ready to launch the GUI:

From your pcsx folder run:
See numerous pcsx threads for settings: the main ones are GPU_UNAI, CPU clock speed 57~100% and 'disable dynarec OFF'

ATM sound is not working because of a missing plugin.