PsNee modchip installation guide

The PsNee modchip is a newer chip that has been under development during the last couple of years, and is still under active development. PsNee modchips should work with every version of the PlayStation 1. They can be made using many AVR processors, including the Arduino Uno, Arduino Pro Mini, ATtiny85, and ATtiny45. This guide covers everything you need to know about choosing, programming, and installing a PsNee modchip into your PlayStation.

If you are looking to purchase a PsNee 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 PsNee 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.

PsNee modchip installation diagrams

MM3 modchip

Below is a list of all PlayStation 1 motherboard versions, 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-7501).

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 PU-22 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.

  • PU-7
    • All SCPH-1000's
    • Some early SCPH-1001, and SCPH-1002's
    • Some early SCPH-3000's
    • Some early SCPH 3500's
  • PU-8
    • Most SCPH-1001, and SCPH-1002's
    • Most SCPH-3000's
    • Most SCPH-3500's
    • All SCPH-5000's
  • PU-16
    • All SCPH-5903's
  • PU-18
    • All SCPH-5001's
    • All SCPH-5500, SCPH-5501, SCPH-5502, and SCPH-5503's
    • All SCPH-5552's
    • Some early SCPH-7000, SCPH-7001, SCPH-7002, and SCPH-7003's
    • Some early SCPH-7501's
  • PU-20
    • Most SCPH-7000, SCPH-7001, SCPH-7002, and SCPH-7003's
  • PU-22
    • All SCPH-7500's
    • Most SCPH-7501's
    • All SCPH-7502, and SCPH-7503's
    • Some early SCPH-9000, SCPH-9001, SCPH-9002, and SCPH-9003's
  • PU-23
    • Most SCPH-9000, SCPH-9001, SCPH-9002, and SCPH-9003's
  • PM-41
    • Earlier SCPH-100, SCPH-101, SCPH-102, and SCPH-103's
  • PM-41 (2)
    • Later SCPH-100, SCPH-101, SCPH-102, and SCPH-103's


PsNee modchip drawbacks

The biggest problem with PsNee chips is that they aren't very well documented (in terms of things like installation diagrams for every board revision). They also can be hard to find for sale.

This guide, along with my store, will help alleviate both of these issues by providing installation diagrams, and a place to purchase the chips.

PsNee modchip advantages

The greatest strength of the PsNee modchip is the fact that it's much more modern than PIC based modchips. Using AVR chips means that programming a PsNee chip is much easier, and many people may already have something like an Arduino which can be used as a PsNee modchip.

Using more powerful processors allows the modchip to work with American, European, and Japanese PlayStation 1's with a single chip, no need for a version for each region. It can even patch the SCPH-102's BIOS to allow playing imports (previously this was only available with the OneChip). Note that this BIOS patch only works with ATmega based PsNee chips.

Going forward PsNee modchips will likely become the new standard modchip, especially as the PIC12C508A chip used for more popular chips like the MM3 reaches end of life.

PsNee modchip source code

If you'd like to program your own PsNee modchips you'll need the source code. It supports the following microcontrollers:

  • Arduino Pro Mini (8MHz, or 16MHz) - supported and tested
  • Arduino Uno (8MHz, or 16MHz) - supported and tested
  • ATtiny85 - supported, untested
  • ATtiny45 (8MHz internal oscillator) - supported, tested
  • ATtiny25 - supported tested

These chips fall into two categories, ATmega based chips, and ATtiny based chips. ATmega chips cost more, but allow for BIOS patching for SCPH-102 systems, as well as debugging for developers. ATtiny chips cost less, but lack those two features. ATmega chips are also considerably larger in size, making them more difficult to fit into a system when compared to the ATtiny chips.

I'm currently working on developing and testing modifications to the PsNee code to support full BIOS patching functionality with some of the ATtiny chips with more than 8 pins.

The source code is available on the PsNee Github page. It can be compiled very easily using the Arduino IDE.

All PsNee chips I sell are preprogrammed.

Where to buy PsNee modchips

I sell preprogrammed PsNee 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 PsNee 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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March 20, 2020 7:13 PM

Hello, I just ordered from you and succesfully modded my PsONE,
A tip for future installers, After soldering, my psone wasnt fully booting every time, the cd motor was spinning way too fast and not reading cds, what happened was that when I soldered the vias points, my wire went too long on the other side of the board and was touching the metal shield causing a short, after cutting the excess wire, no more issues!! excellent modchip!

Matt Christy
Matt Christy
May 29, 2019 6:25 PM

This is probably a noob question, but is the PsNee a SOIC or MSOP/(T)SSOP pinout type? I want to use a breakout board for cleaner installs. I know the Mayumi v4 will support. Thanks!

June 28, 2019 7:17 AM

Hi, I bought the Psnee modchip and installed it n my Japanese PS1 SCPH-7000 but it is only playing original and backup japanese games only. Am I missing something?

July 10, 2020 5:46 PM
Reply to  William Quade

hi, so a SCPH-1000 wouldn't have any problems right?

July 7, 2020 6:48 PM

DigisPark is compatible to program?

July 12, 2020 2:48 PM

Is this possible to replace PSIO in the future? The reader emulation has become so popular since it was introduced in DreamCast and I wonder if this could do the same in the future, without depending on PSIO

May 3, 2021 8:07 AM

Hi there. I just got the PSnee from you about a week ago. Thanks for the quick shipping. Im pretty noob with this and this will probably be a basic question, but I'd like to install this on what would be the easiest of my systems to say. I have SCPH 7501 March 1999, SCPH 1001 March 1996, and SCPH 101 OCT 2000, so if you could suggest which is probably the easiest to install the modchip in I'd appreciate it very much. I haven't looked at the diagram/s yet, and I'm thinking the process might be somewhat streamlined throughout,… Read more »

May 4, 2021 1:22 PM
Reply to  William Quade

Thanks a bunch for the reply William. That's probably going to be my best bet. Lookin forward to getting this installed. 🙂

Last edited 10 months ago by Steve
May 21, 2021 2:24 PM

are there chips that are compatible with a 5500 model bios that i can get and flash a new bios? i don't have a backup ps1 and want to put the american bios on my japanese ps1.

August 21, 2021 11:15 PM

Hi I'm trying to use a psnee on attiny 85 without success .I already compile the psnee with arduino and I got a hex file to program with a tl866 programmer I chose program as a Intel hex after that I disabled ckldiv 8 fuse I'm installed in a ps one pm41 NTSC and doesn't work I was thinking maybe the optical was bad but is not i installed a mm3 that I bought from you a time ago on eBay and that works.Any suggestions

February 22, 2019 12:33 PM

I installed the TL866 Minipro Software on my computer and it does open the ino file for PSNee, but do I install it directly or do I have to install Arduino IDE in order to extract it?

February 22, 2019 2:10 PM
Reply to  William Quade

I'm not sure how to do that, and I don't own a Arduino Board. I only installed the software but I keep getting an error.

February 22, 2019 2:34 PM
Reply to  William Quade

Never mind. I found it.

February 22, 2019 2:45 PM
Reply to  William Quade

Did that. Getting Error Select a board.

February 22, 2019 2:51 PM
Reply to  William Quade

So the steps after installing the Attinycore is to uncomment the
#define ATTINY_X5 line

I guess it worked as I have a hex file now. Thank you.

May 15, 2019 8:04 AM
Reply to  William Quade

Hello William, I managed to do this via arduino nano. I have also tried this with an ATTiny45, but no luck. Can you please let me know if i am doing this right: I have an Arduino Uno and I am trying to upload via the IDE. I have used this pinout (- the capacitor): I did not flash a hex file. 1.I can compile the hex file, but I cannot flash the hex file via avrdude. I get an error saying that the signature of the device (000000) does not correspond to the the signature of the attiny45.… Read more »

May 15, 2019 9:07 AM
Reply to  William Quade

I have an USBasp V2 and I could also use that... form all the tutorials i have seen selecting the 8mhz internal from the arduino IDE and burning the bootloader should fix it... By the way, I used this as an example:
it worked with the arduino nano as modchip, but it won't work with the attiny45 chip :((((

What kind of programmer are you using?