Mayumi v4 modchip installation guide

Mayumi v4 modchips aren't quite as popular as MM3 chips, but may potentially be a better option for most systems. They aren't compatible with older PS1 models, but are compatible with systems starting with the SCPH-5000 (PU-18 and later board revisions). They can be made using PIC12C508A chips. This guide covers everything you need to know about choosing, programming, and installing a Mayumi v4 modchip into your PlayStation.

If you are looking to purchase a Mayumi v4 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 Mayumi v4 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.

Mayumi v4 modchip installation diagrams

Mayumi v4 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 (if the board is compatible).

  • PU-7 (not compatible with Mayumi v4)
    • All SCPH-1000's
    • Some early SCPH-1001, and SCPH-1002's
    • Some early SCPH-3000's
    • Some early SCPH 3500's
  • PU-8 (not compatible with Mayumi v4)
    • Most SCPH-1001, and SCPH-1002's
    • Most SCPH-3000's
    • Most SCPH-3500's
    • All SCPH-5000's
  • PU-16 (not compatible with Mayumi v4)
    • 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

Mayumi v4 modchip drawbacks

There are a couple of downsides to using a Mayumi v4. First of all it isn't compatible with every PlayStation 1 model, so if you have an older console you'll need another chip. Mayumi v1.1 chips are compatible with those older PU-7 and PU-8 boards, I'll be making a guide for those chips in the future.

Another small downside with the Mayumi v4 is that it typically involves installing more wires than other chips like the MM3. In particular for most PS1 models pin 2 isn't required, but it is for the Mayumi v4. Since this is the clock pin for the chip, it's very susceptible to interference which can make it a trickier chip to install.

I've also noticed that there is much less information about Mayumi chips online, and fewer places to buy the chips. This guide aims to solve the information problem once complete.

Mayumi v4 modchip advantages

The Mayumi v4's greatest strength is its reliability. Because the Mayumi v4 uses the timing coming off of the PlayStation 1's board, instead of the internal PIC oscillator (like the MM3 uses) it can boot games more reliably. A Mayumi v4 chip is less likely to get out of sync with the console when booting, meaning that you won't have to restart the console to boot.

Of course this is only the case if pin 2 (the clock pin) is short and well routed (to prevent interference).

Mayumi v4 modes of operation

The Mayumi v4 modchip can operate in several modes. Modes can be toggled by pressing and holding the reset button for at least two seconds. For the PU-22 and PU-23 there really isn't any reason to switch modes. In the PU-18 and PU-20 switching the mode to disabled would be useful if you wanted to play a genuine anti-modchip game that doesn't work in the default mode.

For PU-18, and PU-20:

  1. Mayumi v0.9 mode (default) (supports many anti-modchip games)
  2. Mayumi v1.0 mode (supports many anti-modchip games)
  3. Old modchip mode
  4. Disabled mode

For PU-22, and PU-23:

  1. PU-22/PU-23 strongest mode (default) (supports all anti-modchip games)
  2. Old modchip mode
  3. Disabled mode

Mayumi v4 modchip source code

If you'd like to program your own MM3 modchips you'll need the source code. I have the compiled hex source code for the PIC12C508A.

The Mayumi v4 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. Mayumi v4 PIC12C508A USA
    2. Mayumi v4 PIC12C508A EUR
    3. Mayumi v4 PIC12C508A JAP

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

All Mayumi v4 chips I sell are preprogrammed.

Where to buy Mayumi v4 modchips

I don't sell Mayumi v4 modchips on eBay. Running the high speed clock line successfully was too difficult for many of my customers resulting in a lot of returns. I do still sell them on my own store on this website though.

I currently only ship chips to the United States. If you're located in another country I recommend trying to find a local seller since shipping costs can be expensive.

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

I sell both premodded PS1's, and Mayumi v4 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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November 1, 2018 8:35 PM

Hi there,
Do you still make premodded systems?
I live in Toronto Ontario Canada. I would want a premodded system delivered, e-transfer of funds would be ideal for me.

March 29, 2019 8:47 PM

I’m sure I sound very dumb, but what exactly does the mod chip do?

November 4, 2019 7:25 AM

Hello dear friend,

I have a PS1 scph 7000 japanese. My question would be if I can use the modchip I can use ANY region cd's?

For exemple: Use USA region, EU region and JP region copy cds.

Best Regards

November 26, 2019 7:57 AM

Hi. I have a dead scph 9001 ntsc u. A friend gave it to me. I noticed that it has a chip 12C508A. Now i bought an Scph 7000 ntsc J, not modded. Is it ok to use the chip from the 9001 to my 7000?
Pls note that my 7000 is a PU20. And the 9001 is a PU23.

November 30, 2019 11:30 PM
Reply to  William Quade

Thank you for that advice... I did manage to find a modchip from another of my dead ps1. More specifically psone scph 103 ntsc-j. So the modchip is the same one, 12c508a. Since it was from an Ntsc-j i assumed that if i install it to my Ps1 Jpan, also an Ntsc-j, that the mod would work.. unfortunately, it did not. I tested a backup of my Metal Gear Jpn and it didn't boot..

Michael J
Michael J
March 12, 2020 9:58 PM

Thanks for all the great info, I made a graphic for my own reference about programming a PIC12C508A chip with a PicKit 3, here's a link, might be useful if you ever make that flashing tutorial.