Is it normal that hashrate per card decrease with more GPUs attached to single MB ?
I have 3 systems for testing, each with 4/5/6 GPUs configuration running on identical HW, SW.
Each card is attached via powered riser (they are not all same, different batches) to PCIe x1 slot.
I can see that system with 4 cards performs best in the meaning of hashrate per card, 2nd is 5GPU and 3rd is 6GPU.
Difference on equihash algo with ccminer 2.2.0 on linux is ~10% (best/worst).
What could be a bottleneck ?
It is not really a problem but I would like to know why it performs like that.