Thus bit 0 has to be set, bits 1 and 5 cleared. Value AAh become 89h. BIOS Control (BIOS_SPI_BC) – Offset dc - 1.2 - ID:615146 | Intel® 400 Series Chipset On-Package Platform Controller Hub
But here’s the catch… bit 1 can’t be cleared until the “PLTRST#” (total reset) event is occured. And this bit doesn’t allow to clear bit 5.
The main question is how to perform the total reset without the laptop being shut down? If the laptop is restarted, the BIOS will lock itself again. Sad to admit, but the answer is nohow. The BIOS region is not writable until the CPU enters the SMM state, which occurs when official update starts.