The PS4 motherboard contains two separate firmware slots: an (current version) and an inactive slot (the previous version). When you update your console, the new firmware is installed to the inactive slot, which then becomes active.
Because this is a hardware-level modification, a "downgrade tool" is actually a collection of specialized electronics and software. Tool Category Specific Examples Teensy 2.0++, 4.0, or 4.1 Interfaces with the console's chips to read/write data. Interface Adapters CH341A USB Programmer, CH340G UART-TTL Connects the PC to the PS4 motherboard for data dumping. Software Suites PS4 Wee Tools , PS4 Syscon Tools Patches the dumped firmware files to enable the revert. Physical Tools Soldering iron, flux, 99% isopropyl alcohol downgrade tool ps4
You can typically only revert to the previous version that was installed on your specific console. You cannot jump back to an arbitrary version (like 9.00) unless that was the version immediately preceding your current update. Essential Downgrade Tools & Hardware The PS4 motherboard contains two separate firmware slots:
A PlayStation 4 (PS4) firmware downgrade is not possible through standard software menus or simple USB updates. Instead, users must utilize a specialized hardware process known as . How PS4 Firmware Reversion Works Tool Category Specific Examples Teensy 2
How to Revert the PS4 to a Previous Firmware (Full Tutorial)