1. Make sure your USB flash supports "UEFI boot". (You can refer to below URL for "how to make UEFI Bootable USB Flash".)
http://www.eightforums.com/tutorials/15458-uefi-bootable-usb-flash-drive-create-windows.html
2. Unzip the BIOS package to the USB flash (in this example, the BIOS pacakge is 131123.rar).
The content of the USB Flash as below:
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3. Remove all boot device
4. Plug the USB flash into V20
5. Power on the system
6. System will boot to UEFI mode
7. Type “ fs0: ” (the path of the USB flash) and press Enter
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8. Type afuefix64p.efi 131123.rom /p /b /n /x to update the BIOS
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9. When BIOS update finish, restart the system