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kalymos edited this page Apr 19, 2026 · 56 revisions

MCU currently supported.

MCU Arduino
ATmega328/168 Uno/Mini/Mini Pro
ATmega32u4 Leonardo/Micro/Micro Pro
ATtiny25/45/85*

*Not compatible with the BIOS patch

The oversimplified way to do it

  • Choosing your compilation options.
  • Compilation.

Note

With the new BIOS patch implementation, specific fuse configurations are no longer a major issue. The timing is much more flexible than before.

The only critical setting to check is the Brown-out Detector (BOD), which should be set to 2.7V.

• Injecting the code into the target.
• Soldering the modchip according to the diagrams.

Find out if my console needs a BIOS patch

The BIOS patch is required for certain models to bypass regional lockout and play import games.

Regional compatibility details:

  • Japanese Models (SCPH-xxx0 NTSC-J):
    • BIOS patch REQUIRED to play American (NTSC-U/C) games.
    • Cannot play European (PAL) games without additional hardware clock modifications.
  • American (SCPH-xxx1 NTSC-U/C) & Asian (SCPH-xxx3 NTSC-J):
    • Can play each other's games (NTSC J/U) without a BIOS patch.
    • Cannot play European (PAL) games without additional hardware clock modifications.
  • European Models (PAL):
    • PS One (SCPH-102): BIOS patch REQUIRED to play American (NTSC-U/C) and Japanese (NTSC-J) games.
    • Fat Models (SCPH-7002, 7502, 9002): With motherboards PU-20, PU-22, or PU-23, these can play NTSC-U/C and NTSC-J games WITHOUT a BIOS patch or clock mods.
    • Older Fat Models: Require a hardware clock modification to correctly run NTSC games.

Important

If your console is a Japanese SCPH-xxx0 or a European PS One SCPH-102, you MUST use the ISP method to inject the code. Standard USB upload cannot handle the BIOS patch.

Personal recipe to make a good PSNee via ISP

When can I use simple USB injection?

You can use the direct USB injection method ONLY if:

  1. Your console does NOT require a BIOS patch:
    • All American models (SCPH-xxx1).
    • All Asian models (SCPH-xxx3).
    • All European Fat models (SCPH-1002 to 9002).
  2. AND you are using an Arduino board with a bootloader (like a Nano or a Pro Mini with an FTDI adapter).

Tutorial for injections via USB

Pinout MCU & Arduino

Motherboard diagram

BIOS diagram

To determine your BIOS version, which is essential for old Japanese models, the BIOS dumper project works very well.

BIOS diagram

Other diagrams

PsNee Modchip Advantages

The PsNee modchip uses AVR microcontrollers instead of the older PIC-based architecture. This allows for easier programming and the use of common Arduino boards as modchips.

The increased processing power enables support for American, European, and Japanese consoles with a single code base. It also allows for BIOS patching to bypass regional lockouts on specific models (SCPH-102 and Japanese models).

PsNee Modchip Drawbacks

Because of the diversity of PS1 motherboard revisions and regional requirements, the code must be configured and compiled specifically for each setup. There is no single universal pre-compiled file.

Microcontroller Categories

The supported chips are divided into two categories:

  • ATmega-based (e.g., ATmega328P, 168, 32U4):
    • Features: Supports all features, including BIOS patching. Can be programmed via USB if a bootloader is present.
    • Physicality: Larger footprint, requiring more space inside the console.
  • ATtiny-based (e.g., ATtiny25/45/85):
    • Features: No BIOS patch support. Limited to standard modchip functions. Always requires an ISP programmer for code injection.
    • Physicality: Very small size, allowing for easier integration on the motherboard.

PAL and NTSC incompatibility with your TV

The PlayStation 1 output signal (PAL or NTSC) is determined by the region of the game being played. While the modchip unlocks the console's ability to run any game, it cannot change how your TV handles the signal.

This is primarily an issue with CRT (cathode-ray tube) TVs:

  • North America & Japan: Most CRT TVs only support NTSC signals. Running a PAL game will often result in no image, a rolling screen, or a black-and-white picture.
  • Europe: Many European CRT TVs (especially later models) support PAL60, allowing them to display NTSC games in color.

Solutions:

  • Composite-to-HDMI converter: These affordable devices convert the specific analog signal (PAL or NTSC) into a standard digital HDMI signal compatible with any modern flat-screen TV.
  • RGB Scart Cable: For CRT users, using a true RGB cable can often solve the black-and-white issue on compatible TVs, though it won't fix screen rolling if the TV cannot sync to the frequency (50Hz vs 60Hz).

Japanese consoles and video glitches with PAL games

Japanese consoles with specific clock signals can produce a bad video signal when playing PAL games. A known solution.

Things just for curiosity

Home

Personal recipe to make a good PSNee via ISP (complete tutorial for all possibilities)

Tutorial for injections via USB, only for ATmega without BIOS patch!

Pinout MUC & Arduino

Motherboard diagram

BIOS diagram

Other diagrams

BIOS Dumper 2.6

Video tutorial

Why it doesn't work!

The rest is for curiosity

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