[quote user="JGarcia"]Do I have to load gel file for every core?[/quote]I haven't got a TMDSEVM6678LE to try but:
1) Connecting To An LCEVM with CCS suggests a GEL file should be loaded for each core used.
2) Looking at ..\..\emulation\boards\evmc6678l\gel\evmc6678l.gel shows the script only initializes the PLL and DDR3 when run on core 0.
Therefore think that the ..\..\emulation\boards\evmc6678l\gel\evmc6678l.gel needs to be selected on all cores which will be used, and core 0 must be connected first to initialize the PLL and DDR3.
[You will probably get a more definitive answer on the Keystone Multicore Forum]