Sony uses (electronic fuses) on the console’s motherboard. Every time you update your firmware, the system burns a specific physical fuse inside the Syscon (System Controller) chip. When you try to boot, the Syscon counts how many fuses are blown. If you attempt to install a lower firmware (9.00) than the current fuse count (set by 10.50), the Syscon sees the mismatch and refuses to boot . This is an immutable hardware lock.
: This process requires soldering tiny wires directly onto the PS4 motherboard. High-Level Steps ps4 downgrade 10.50 to 9.00
Searching online will find “PS4 downgrade tool” or “9.00 firmware installer for 10.50”. These are : Sony uses (electronic fuses) on the console’s motherboard