Although PSX Emulator does not need any plugins to work, it is necessary to install it in BIOS for the first play. The big guys in the category are two older projects that haven't released a newer version since 2008 – pSX and ePSXe. All that pSX need in order to properly run, as most of the emulators, is a.I recommend you try out the excellent RAM hacking tool called CheatEngine.
You can find codes quickly with any emulator...
Using the emulator pSX, you can use GameShark codes if you:
A. Boot a GameShark v5.0 disc, then the game
Cep Psx V1 13 Codex
B. Boot a CodeBreaker disc, then the game
Cep Psx V1 13 Emulator
Cep Psx V1 13 0
NTSC Disc that runs NTSC and PAL GameShark Codes
PAL Disc that runs NTSC and PAL GameShark Codes
Sites that have GameShark/Xploder/CodeBreaker codes for PlayStation 1:
And for Guides and Saves: