PU-22 PsNee modchip installation diagram

This is my favorite version of the PlayStation 1. It’s in newer systems, so the lasers are more likely to still be in good condition, but the system still has both the serial and parallel ports on the back. This board was used primarily with the SCPH-7500 series of systems.

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

PU-22 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-22 PsNee installation diagram

Above is the diagram for the PU-22.

This diagram is fairly straightforward. Be careful when soldering to the capacitor that connects to VCC and GND. In particular, the GND point can easily be bridged to nearby pins/pads.

Installation tips

Here are some tips I have for you when you are soldering your chip into the PU-22.

  • 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.
  • Placing the chip on top of the chip in between SUBQ, SQCK, GND, and VCC is a good spot.
  • Watch out for solder splatter when you are desoldering the metal shield on top of the board. It isn’t necessary to put it back on, but I always do.

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.

  • Jon Co

PU-22 PsNee example installation

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FoDWilliam QuadePreto FonsecaEJackMr. Metric Recent comment authors
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I don’t have a vcc called pin on my Arduino nano is there a different name for it?

Jon Co
Jon Co

I just installed this based on the instructions. Looks like the Vcc/Gnd has the polarities reversed in your diagram.

Mr. Metric
Mr. Metric

I tore off the GATE_WFCK pad. Is there anywhere else I can connect the wire?


This happened to me as well, so I soldered directly to the pin with flux by having as few solder as possible on the tip and soldering a single strand from a multistrand copper wire
Tricky, but that worked

Preto Fonseca
Preto Fonseca

Here’s my contribution, using a Attiny85. The only difference being that i took ground from other pad.


Okay, I just did some testing with the Attiny85 and it does not play nicely with something like Tony Hawk Pro Skater 2, and it did not boot the backup. I will have to order some 45s or use the Mayumis I ordered from you.