It could be due to the reduced number of PCIe lanes on Pentium and Celeron CPUs.
More CPU cores also helps reduce latency with a large number of GPUs to manage.
i have g4400. it support 16 pcie lines. z270 chipset support 24 pcie lines. so what can be problem? ram? 4 gb i will try with 8 gb(4gbx2). also i can try with i5-6500 but it supoort 16pcie lines too. i dont think it worked.
but i am trying to run 14 gpu. any help would be appreciated...