: Crucial: Never flash firmware designed for the international version (i9300) on a Sprint S3. This is a common cause for "hard-bricking" the device because the processors (Exynos vs. Snapdragon) and radios are entirely different.
: If the bootloader is completely destroyed, specialized JTAG unbricking services are the final resort for physical hardware repair. Sprint Firmware Galaxy S3
While physical manuals are rare now, the following community resources act as the definitive "papers" for this device: : Crucial: Never flash firmware designed for the