MM3 modchip installation guide

MultiMode 3, or MM3 modchips are very popular, and should work with every version of the PlayStation 1. They can be made using PIC12C508A, PIC12F629, and other PIC chips. This guide covers everything you need to know about choosing, programming, and installing an MM3 modchip into your PlayStation.

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 MM3 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.

MM3 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


MM3 modchip drawbacks

The biggest problem with MM3 chips is how they 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.

MM3 modchip advantages

The MM3’s greatest strength is its compatibility and popularity. From my experience it is the single most popular PS1 modchip being used today. Because of this you’re more likely to find people who can help you if you are having problems installing your chip.

Additionally the MM3 is compatible with most PS1 consoles and can play anti modchip games if you install all seven wires. The only system that you definitely shouldn’t install an MM3 in is the SCPH-102 (install a ONEchip instead).

MM3 modchip source code

If you’d like to program your own MM3 modchips you’ll need the source code. Right now I only have the code for the PIC12C508A and the PIC12F629. If you have the code for other PIC chips let me know and I’ll add them to this post.

The MM3 chip has three different versions, one for each region. If you have an American system use the USA version, if you have a European system use the EUR version, and if you have a Japanese system use the JAP version.

  1. PIC12C508A
    1. MM3 PIC12C508A USA
    2. MM3 PIC12C508A EUR
    3. MM3 PIC12C508A JAP
  2.  PIC12F629
    1. MM3 PIC12F629 USA (assembly source)
    2. MM3 PIC12F629 EUR (assembly source)
    3. MM3 PIC12F629 JAP (assembly source)

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

All MM3 chips I sell are preprogrammed.

Where to buy MM3 modchips

I sell preprogrammed MM3 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.

I also sell these same chips at a slightly higher price on my eBay store.

I currently only ship chips to the United States. If you’re located in another country I recommend buying from EurAsia. They sell genuine chips for a good price, but shipping is fairly slow.

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

I sell both premodded PS1’s, and MM3 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 24, 2020 8:06 AM

What type of solder and flux do you use?

Matt McGuffey
Matt McGuffey
April 23, 2020 1:32 PM
Reply to  William Quade

Hi William!
Can you additionally suggest a good and reliable fine point soldering gun? Just got my MM3 in the mail from you. Excited to install and rebuild my old JP library I had in high school 🙂

September 14, 2020 9:19 AM

Hello 🙂 I followed your guide and successfully modified my first console (scph9002)
Thank you so much for your advice

May 2, 2018 2:57 AM

If I’m interested in trying to program my own mm3 mod chip, do you have a recommended PIC programmer? Did you buy one or make one from scratch? What software do you use for the .hex files, etc? How do I verify that it worked correctly, before soldering it to a PS1.

Thanks in advance. Love the site.

Felipe Chierice
Felipe Chierice
May 2, 2018 11:50 AM

Hi Quade, nice guide!

I have a question, can I write the 12C508A program code into a 12C509A microcontroller, and use the same wire diagram? Thanks for your attention.

Felipe Chierice
Felipe Chierice
May 2, 2018 9:12 PM
Reply to  William Quade

Excellent then, thank you very much for the quick reply! I’ll work on it next weekend and give you a feedback.

Christopher Spies
Christopher Spies
April 5, 2019 7:00 PM

Does the mm3 come pre programmed I am just wanting to be able to play my ntsc PlayStation so I can play Japanese games on ntsc

Christopher Spies
Christopher Spies
April 5, 2019 8:11 PM
Reply to  William Quade

Which one will I need I have a nstc scph-1001 PlayStation so I can go ahead n order the chip

christopher spies
christopher spies
April 5, 2019 8:27 PM
Reply to  William Quade

So I need to order the psnee chip n is there a diagram on ur website for 1001 playstations

April 24, 2019 12:04 PM

The Pic12C508A is recognized by my TL866. Any special way to load and write the hex file? Thanks.

April 25, 2019 6:02 AM
Reply to  William Quade

Cool, just like my SNES projects! Thanks.

May 17, 2019 5:38 AM

How to program 12С508 with programmer K150? I did not succeed, it just does not work

October 28, 2019 7:07 PM

hello good site a question also serves the 12C508 / P?

February 13, 2020 9:51 AM

What does each pin do exactly for this modchip? Interested in technical details. I got it installed first try so loving it!

March 5, 2020 9:41 AM

Hello, I installed the MM3 chip in my PU23 board and when I boot up the PS1 it takes me to the audio CD/memory card screen. I didn’t connect pin 2 to anything and connected pin 4 to pin 1. Any ideas what could be wrong?

June 25, 2020 11:53 PM

i have PIC 12F675 can i download MM3 PIC12F629 Hix file and work for 12F675
or i must buy PIC 12F629
what a programmer i can use
thanks for your effort

July 1, 2020 5:09 PM

Hello, I want to buy the PIC12C508A chip and program it myself, what should I do with the code file that you published? And what device should I use to connect the chip to my computer?

July 13, 2020 12:54 AM

has anyone tried to use cheat devices or cheat discs like gameshark with the mm3 chip, i have tested my 3 cheat carts and like 4 cheat discs with all my modded ps1 consoles running mm3 chips, schp-1001, scph-5501, scph-7501, scph-101, all of them will not work with cheat carts or discs, i think it has to do with the way the mm3 chip uses stealth, on power on the chip will send the wobble code for a few seconds and then stop, well when loading up a gameshark and taking time to pick your cheats the time runs out,… Read more »

August 2, 2020 5:12 PM

This chip will allow a japanese ps1 to boot/play american games normally?

August 2, 2020 5:19 PM
Reply to  William Quade

ohhhh nice thanks, so basically this chip works with any japanese model before model version SCPH-3000 right?

August 2, 2020 5:34 PM
Reply to  William Quade

thank you William, I’ll have that in mind if I can’t get an american version.

August 5, 2020 5:52 PM
Reply to  William Quade

do you know of any other chip that will do a japanese ps1 region free to play american games on it? I’ve been told that when you chip a japanese ps1 it will read anything (original and copy games and also original games from any region)

November 7, 2020 8:45 AM

With this chip, ps1 can read cd-rw? If not, is it theoretically possible someday?

November 17, 2020 12:46 PM

hi william,
I recently got 2 PIC12C508A chips and I installed one on a psx scph-5502 following your pattern on PU-18 motherboards and it works perfectly with all types of both backup and original CDs.
The only thing is (but I think it’s a psx model problem) that both USA and JAP NTSC games make me see them in black and white maybe you know why?
one last question: the scheme you published ie the 7-wire mod by chance is the so-called stealth modification?
Thank you. Juri.

November 17, 2020 3:58 PM
Reply to  William Quade

Thank you for the response!
i read somewhere that the 55xx series psx have the oscillator which does not reproduce the 60HZ signal.
i connected the rgb cable and the result is identical. i also tried it on my 2015 lcd tv and same thing.
do you think it is for the oscillator?

November 17, 2020 5:06 PM
Reply to  William Quade

Thank you so much William.
Bye Bye…