Flash QE Bit Fix for RP2350 Boards with PSRAM locking up when overclocking.

A utility that sets the Quad Enable (QE) bit in the flash chip's Status Register 2. This is a permanent fix for RP2350-based boards with PSRAM that use non-Winbond flash chips (e.g. Puya), which lock up when overclocking the RP2350 due to the QE bit not being set from factory.

For example, some batches of the Waveshare RP2350-Pizero ship with Puya flash and lock up when overclocking.

Winbond - working	Not working

Boards without PSRAM are not affected by this issue.

See also PicoPlus-devel/pico-infonesPlus#191

Usage

1. Build the project using the Pico SDK (requires pico-sdk with RP2350 support):

   mkdir build && cd build
   cmake ..
   make

2. Flash the resulting FLASH_QE_SET_1.uf2 onto your board via UF2 bootloader.
3. The program will set the QE bit and print the flash status registers over USB serial.

A prebuilt UF2 is available in the uf2/ directory.

Caveat

Affected boards (RP2350 + PSRAM + non-Winbond flash) cannot be overclocked above 252 MHz, even after applying this fix. The original WaveShare RP2350 Pi‑Zero uses Puyasemi’s 16MB Flash, and once the patch is installed, it can be overclocked to 378MHz to run PCE/MD or SNES emulators.

The FLASH_QE_SET_1.uf2 cannot be applied twice. The second attempt causes the .uf2 update to fail, and you need to use "universal_flash_nuke.uf2" to perform a full FLASH erase before things return to normal. See: https://github.com/Gadgetoid/pico-universal-flash-nuke/releases

Credits

• Original fix by Waveshare.
• Thanks to szuping for testing and sharing the solution.