ATF Now Support 64-BIT Qualcomm CPU MSM8916 for SDC BOOT Repair.
Here is a Galaxy Core Max SM-G5108Q booting via SDC and entering Download Mode: 
Instructions:
1. Download SDC File From ATF Support Site:
ATF Offcial Support Area / file-support / Samsung SDC Files 2. Write SDC File to a 8GB SDHC Micro SD Card via ATF Software SDC Tool
3. Insert micro SD Card to Phone
4. Insert USB Cable to Phone and wait...
You will get Download Mode Shortly
5. Flash Phone with a Firmware same version as SDC File or Higher
