I get errors with 6 RX 580 GPUs
Seems to work fine for 4 GPUs
cl_mem_object_allocation_failure
You ran out of memory. increase the size of virtual memory in Windows. you can see how in the guide below. For instance, say you have 6 Vega GPUs, they have 8 GB of mem each, so you multiply 8x6 equals 48. So you set virtual memory in Windows to 48000MB.Seems to work fine for 4 GPUs
cl_mem_object_allocation_failure
http://vega.miningguides.com/