Changing the BIOS of a Playstation 1 may sound weird. As explained in a previous article, my console is a Japanese model thus it has an additional region check in its bios. So even with a modchip, it can’t boot any game that is not NTSC-J : it reads orignal discs and backups, but only japanese ones. This is why I decided to change the BIOS, and it was also the opportunity to install a flashable BIOS with XBOO.

This is the story of my PSone bios change…

Requirements

Here are the materials I used for this mod :

• A new BIOS chip. I bought mine at https://www.willsconsolemodifications.co.uk. I took it with PSX-XBOO BIOS.
• An hotair gun
• Some heat tape
• A soldering iron with a fine tip (0.2 or 0.15mm)
• Some solder

Replacing the bios

Before processing, the motherboard must be removed from the shell. If you need to check theses steps, I already did it the PSNee installation article. This BIOS is located on the top left part of the motherboard (you can see the installed PSNee modchip just below with black and red wires) :

The easiest way I found to desolder the bios is to use an hot air gun at 400°C. I protected all the components around it before starting to heat the upper part until I could lift up all upper legs. Then I did the same with bottom legs.

Here is a photo with the original BIOS on the left, and the new one on the right. 

As You can see, the new BIOS does not have any legs. Instead, it has some small holes that must be filled with solder. This requires to prepare the pads on the motherboard by adding a bit of fresh solder on each one. Then I put the new BIOS board over the pads and soldered it.

Here is an overview of the motherboard with the new BIOS

XBoo bios screenshots

If you don’t know what the PSX-XBoo BIOS looks like, here are some screenshots of all menu entries. It is quite austere regarding the official interface, but there are far more options and informations.

The only feature that does not work correctly on my PsOne is the faster card reader : I get corrupted save or not detected card if I set a value other than “0.5 (normal/slow)”