1. Copy .gel file unzip from DP800(ARM)Update(Bootloader) to the root of USB flash
2. Insert USB flash into DP800 (make sure the USB flash can be recognized by DP800). Power on DP800, press and hold HELP button until the update started.
3. Move USB flash after update is finished, then press these button in turn: HELPHELPM4M2M1 (update analog board 1), M4M2M2 (update analog board 2)
4. Reboot DP800 after all the update finished and check the new version (Utility->system info->M1-M3-M2)

DP800(ARM)Update(Bootloader) only used by Rigol AE/FAE, this upgrade file can be used to upgrade the bootloader of DP800(upgrade from 00.01.09.00.01 version(including) to new version), if upgrading failed, it will cause to the DP800 can not boot anymore, then it requests to back to rigols factory to fix. In below situation maybe lead to the upgrading failed:
a) Power off while it is upgrading;
b) The upgrade file is wrong.
c) The usb disk can not be accessed correctly by DP800
Do not update the DP800(ARM)Update(Bootloader) file twice or the unit will fail to start up.