When a device powers on, the internal BootROM (BROM) executes first. It searches for and hands control over to the preloader partition.
When the Preloader is so corrupted that BROM mode cannot be reached through software means, hardware-level tools such as JTAG programmers or ISP (In-System Programming) adapters may be necessary. These tools bypass the normal boot process entirely and write the Preloader directly to the eMMC chip. This is a last-resort option requiring specialized equipment and soldering skills. mtk preloader repair tool