This has been taken care of.

Download the below as zip:

https://github.com/pinkeen/libretro-common-shaders-glsl

extract to pc.

Move wanted shaders to:

[/opt/retropie/emulators/retroarch/shaders/whateverfolder/whatevershader.extension]

I wrote a tutorial a while back with some tips to help with the disc swapping and save state mess. https://retropie.org.uk/forum/topic/19269/tutorial-painless-apple-game-emulation?_=1592965674049

One thing I would like to see is write protect in the emulator. Games written in Apple Pascal need the boot disc write protected or the boot hangs. This includes the first 3 Wizardry games. Like I discussed in the tutorial, you currently need to use file permissions as a workaround for this.

After an evening of pondering this, I have figured out what I did to screw it up. I have created multiple images of RetroPie setups that were reasonably customized and saved piles of things I referred to as "Clean" associated with those. (For example, known good ROMS, BIOS, and Meta Data like Scraper results.)

What happened was that I missed a step trying to recreate my steps. So here's the abbreviated version of what I did that messed it up.

Wrote the correct, unaltered, unupdated 4.5.1 image to the SD card (I really couldn't believe I would have written the wrong image). Copied vast amounts of "Clean" altered configs (for a setup that was designed for SNES controller compatibility, and thus didn't use PSX). Boomie. (At this point, I believe my copying of configs was all it took to scramble it up.)

It should have been obvious when the pixel art launch screens came up (part of the config I just copied), but I honestly recall thinking "Oh cool, 4.5.1 uses the same pixel art things I liked for launching games."

Thus, to your point, I had 4.5.1, with a bunch of 4.4 config wedged in manually after the fact. Worse, because my previously configured system never used PSX (not enough RasPi power when I created it, and not enough buttons when using SNES controllers), I had no idea that there might have been a bug with it that had been hiding in what I was copying.

Thanks for the feedback.

@mitu
Awesome!
Perhaps it's an incompatibility issue related with Ubuntu x64 19.04, will try experiment a bit more, but I'm glad at least it works on the RPi, hopefully someday this code will be added into retropie script since the upstream version has a higher games compatibility than old stella 2014

@BuZz
Is it possible to add this core to retropie?
https://github.com/stella-emu/stella/tree/master/src/libretro

It's the upstream stella, but I am not sure how to compile it as libretro core... so I do not know I it's compatible with arm architecture.

meanwhile, is there any workaround to add it manually ?

The Problem was located:
When using pbp files with sbi files the extension both must be lower or uppercase.
Having them mixed will result in the emulator not finding the sbi file since linux systems are casesensitve.

multidisc PBP Systax is as described in the sourcecode comment above.

Github issue:
https://github.com/libretro/beetle-psx-libretro/issues/241

Has anyone tried it more recently?? I was just curious to know if after more than one year it got better in performances...