PU-23 PsNee modchip installation diagram

The last version of the original PlayStation 1 design was the SCPH-900x. Most of these consoles have PU-23 boards inside. The most notable difference between the 9000 series and earlier consoles is that Sony removed the parallel IO port on the back. They also shrunk down the size of the board significantly.

For more information about PsNee chips click here, for more information about PS1 modchips click here.

PU-23 PsNee modchip installation diagram

PsNee ATtiny45 pinout

Arduino pinout:

  • Pin VCC – VCC
  • Pin GND – GND
  • Pin 3 – Debug TX
  • Pin 4 – BIOS A18
  • Pin 5 – BIOS D2
  • Pin 6 – SQCK
  • Pin 7 – SUBQ
  • Pin 8 – DATA
  • Pin 9 – GATE_WFCK

PU-23 PsNee installation diagram

PU-23 PsNee installation diagram, alternative points

Above are some diagrams for installing the PsNee into a PU-23. The first diagram shows the pinout of the ATtiny45, the second shows the installation diagram (including pin numbers for Arduino users), and the third shows some alternative points. Click on an image to open it in a new tab where you can zoom in to get more detail.

Let me know if any of the points aren’t clear, I can clarify them for you.

Installation tips

Here are some tips I have for you when you are soldering your chip into the PU-23.

  • Cut your wires to be as short and direct as possible.
  • You don’t need to connect pins one and two of the ATtinyX5 chip. Just desolder the wire.
  • Use a multimeter to probe around for alternative VCC and GND points closer to where you position your chip for a cleaner installation.
  • For DATA, be careful not to bridge the connection to the other resistor next to the one you are soldering to.
  • Don’t apply too much solder to SQCK, or you’ll bridge the pins on the chip.
  • For the wires that go into the holes, or vias, of the board: it’s easiest to stick a small 30 AWG wire through the hole, then heat the wire and hole while adding solder.
  • Placing the chip on top of the chip above SUBQ and SQCK is a good spot.

Diagram success rate

Here’s a list of people who have successfully modded their console with this diagram. Leave a comment and I’ll add you to the list.

  1. William Quade (me)

Example installations

This section has photos of some successful installations which you can use to get a better understanding of how everything is wired and positioned.

  1. William Quade (me)

PU-23 PsNee example installation

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stonedmasterWilliam Quadebobmalhansboniniscypax Recent comment authors
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I hope it helps someone:
If you want to use an arduino nano, you have to erase the bootloader. To erase the bootloader you have to write the code with an isp if not it is not going to work.
i’m leaving on this link some pics of te instalation i made
link: https://mega.nz/#F!DGIygCbD!hTUX5TXdciOeCU9eNkX5hw


Elsalas55 thank you!


I accidentaly remove the resistor on data connection… anybody knows the value for him?


Do you have any idea why can’t read my scph-9002 any NTSC game? It just stuck on the second screen. My another scph-7502 with psnee plays any of these disks. And It can’t be nor laser or disk problem because it is reading easily crappy audio discs and I played some PAL games on it without any problem. I’ve used the same psnee code on both of them with an arduino mini.
Thank you for any advance!


Heres a pic of my install