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I have successfully bridge the last PCIe lane to produce additional 3 PCIe. lane using PCIe Splitter adaptor, from the original 1 PCI lane and 2 PCIe lane we have make this possible, with no issue running 5 GPU at the same time.
from this test experiment we use the following parts:
H61 Motherboard + Intel Pentium G2XXX series from 3 Pcie lane successfully Expanded Pcie late to 5 Pcie lane. Running 5 GPUs.
#SuccessfullyBridgePCIeLane
if your interested gettting 1 PCIe to 3 Pcie Splitter adapter
here the link on how you can get one.
https://www.facebook.com/commerce/products/1299695706817968/