ONEchip modchip installation guide

ONEchip modchips were designed specifically for PAL PSone slim consoles. They patch the additional region locking in the BIOS of these systems. They can be made using PIC12C508A, and other PIC12 chips. This guide covers everything you need to know about choosing, programming, and installing a ONEchip into your PlayStation.

If you are looking to purchase a ONEchip modchip they are for sale in my store.

Guide structure

This guide is structured into several pages. It's organized like this primarily so that comments can be more organized and useful for readers.

This page covers the ONEchip modchip. It includes general information about the chip, and then links off to installation guides for each console model.

If you want more information about PlayStation 1 modchips in general check out this guide.

ONEchip modchip installation diagrams

ONEchip modchip

Below is a list of all PlayStation 1 motherboard versions (at least the ones that are compatible with ONEchip), along with the console model numbers associated with them. You can get a good idea of what board you have by looking at the model number underneath your system (something like SCPH-102).

To actually know what board you have you'll most likely have to open up your console and look for the board version printed somewhere on the board (something like PM-41 (2) or PM-41).

Once you know what board you have you can click on the board model and you'll be sent to a page with the installation diagram.

  • PM-41
    • Earlier SCPH-102, and SCPH-103's
  • PM-41 (2)
    • Later SCPH-102, and SCPH-103's


ONEchip modchip drawbacks

The biggest problem with ONEchip chips is that they are only compatible with PAL PSone consoles.

They also base their timing on the internal oscillator within the PIC chips. Using the internal oscillator can sometimes cause the chip to become out of sync with the console when booting, meaning you'll have to restart the console to boot.

Certain PIC programmers can also mess up the internal oscillator value when programming, which could be a problem if you are programming your own chips. Additionally it has been reported that certain batches of PIC chips have had problems with the oscillator value in the past.

ONEchip modchip advantages

The biggest advantage of the ONEchip is that they are one of the only chips that allows you to play non-PAL games on a PAL PSone. The other compatible chip is the ATmega based PsNee chip.

ONEchip modchip source code

If you'd like to program your own ONEchip modchips you'll need the source code. Right now I only have the code for the PIC12C508A.

  1. PIC12C508A

I'll have a tutorial on how to program these PIC chips in the future.

All ONEchip chips I sell are preprogrammed.

Where to buy ONEchip modchips

I sell preprogrammed ONEchip modchips on my store. The shipping is calculated by weight so if you buy more than one chip at a time you'll be able to save some money.

Where can I get premodded systems, or have my console modded?

I sell both premodded PS1's, and modchip installation services on my eBay store, as well as my store on this website.

On my store you can select which chip you'd like, and which model of console you'd like. On my eBay store I use a single product listing for every model of console and every type of chip, and update the title and description to reflect what is currently for sale.

More information is available on the linked listings.

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January 27, 2021 5:53 PM

Just programmed this hex to a 12C509A, works perfect

Ivan Timofeev
Ivan Timofeev
February 21, 2019 2:29 AM

We are waiting for the firmware.

January 1, 2020 6:41 PM
Reply to  William Quade

Was this ever ported over to the 12f629 chips?

January 8, 2020 4:31 AM

So this is the chip I'd need for my PAL Australian scph 102?

December 11, 2020 12:44 AM

One chip hex here is for europe?

December 19, 2020 7:17 PM
Reply to  William Quade

Nice, I just programmed your hex file for one chip on the pic 12c508a, time to install it on scph-102 (pm-41/2) 😁
Thanks for letting me know more about the electronics 👍👌

February 23, 2021 2:46 PM

Trying to program this to a 12f508 but keep getting 'out of address of device' error, does anyone know how to fix this? I'm using the tl866 ii plus and xgpro software, thanks

February 24, 2021 12:05 PM
Reply to  William Quade

Ah ok, I had read that they were practically identical so assumed the same hex worked on both chips, could you point me to a hex that works with the 12f508 please?

Last edited 1 year ago by Jamie
March 2, 2021 5:14 PM
Reply to  William Quade

Found the issue, the software was missing the last address line when 12f508 selected, I programmed it under 12c508 and manually entered the oscillator value and it works now

August 20, 2021 11:12 AM

I have a new modchip for this version
it's quite reliable, seems to pick up the injection strings a lot quicker on some games on this ASM version (as oppose to the arduino one)

I'd be more than happy for you to stock these and sell with just a mention of "vajskids consoles'
Btw: I recommended you on a social media platform for a US buyer for premodded system