The file is a critical component of the firmware update for the TP.SK708D.PC821 Go to product viewer dialog for this item.
Copy the .img file to a FAT32-formatted USB drive. Download SK708D PC821 3840X2160 REF52 part02 rar
Extract the files to find the main firmware image, often named allupgrade_aml972_8G_1G_sos.img . The file is a critical component of the