How much RAM I really need for eth mining with 19 GPUs ? (5700 XT 8GB)

Practically all mining tutorials boast that only 4 GB is enough ram for mining. But phoenixminer in hiveOS wont mine and gives "Allocating buffers failed with: clCreateBuffer (-4) " error.

My goal is to mine with 19 GPu with my B250 motherboard and my friend says (he is mining with 19 GPU with same mobo) that I need 16 GB RAM in order to mine efficiently.

could someone verify how much RAM I really need for 19 GPU ethereum mining?

For setup with 19 GPU 8Gb will be recommended
But I’m not sure that motherboard can even start (power on) with 19 AMD GPU on B250. Maybe BIOS update will be needed