I never knew Blender take issues so seriously.. and this much focus and respond from you gurus is really appreciated. This also pushing me to find more bugs to make Blender rule the CG world!. Hat's off everyone!.

I don't' know if I should write here such information or not. I'm using Macbook pro mid 2015. Running Blender all version very smoothly, since the day Apple announced no more Nvidia I was planning to buy Radeon 580. I already have eGPU with nvidia gtx 970. Now when Nvidia is not supported in Apple I installed bootcamp windows 10 and there nvidia runs like a charm for Cycles. I also thought to buy Radeon so I won't need to switch OS every time but cycles may seems not supporting Radeon Rx 580..... Now I think I should also do some practice on Radeon ProRender for Blender that is fully compatible with AMD cards and Blender... I'm not marketing or anyway supporting Radeon ProRender but just a solution to keep using Radeon 580 whoever has this GPU... . I can't leave my GTX 970 btw!.

I'm sorry.. Please ignore this bug or issue. This was my fault.... the resolution division were limited to 32... I raised that and it started simulating now.