Read the manual. There's BIOS flash button at the back that is used to flash BIOS even without CPU.
Updating BIOS with Flash BIOS ButtonBefore updatinglease download the latest BIOS file that matches your motherboard model from MSI®website and rename the BIOS file to MSI.ROM. And then, save the MSI.ROM file to the root of USB flash drive. ImportantOnly the FAT32 format USB flash drive supports updating BIOS by Flash BIOS Button.1. Connect power supply to CPU_PWR1 and ATX_PWR1. (No other components are necessary but power supply.) 2. Plug the USB flash drive that contains the MSI.ROM file into the Flash BIOS Port on rear I/O panel.3. Press the Flash BIOS Button to flash BIOS, and the LED near the Button starts flashing.4. After the flashing BIOS process is 100% completed, the LED would be off simultaneously