Ps1 - Mayumi V4 with Breakout PCB

I HIGHLY Recommend the PSNEE instead of Mayumi as it supports all regions, is an easier install and is more reliable. 

You can grab one HERE

This listing for an Mayumi V4 Modchip for the Playstation 1 (Psone, PS1, PSX)

When installed properly, These chips will allow for Region Free Disc playback as well as Backup support.

This modchip is a 8 wire install and will work on any Ps1 revision except for the early models with the Av Jacks (Pu-7 / Pu-8)

Keep in mind that Pal games will likely have display issues to the 50htz to 60htz differences. 

These chips are programmed to work on North American consoles (NTSC-U) if you have a Pal or NTSC-J console, this will not work for you. 

For install Diagrams I'd recommend checking out Quade's Page Here!