gpu slot on motherboard
DEEPCOOL CH160 - Black Portable High Airflow ...
Sliger SV540 is a Vertical PC case with Mini-ITX motherboard, SFX/SFX-L PSU, 280mm AIO and 3-slot GPU support.
4 PCI-Express x16 Slots Motherboard | Pangoly
BTC-T37 GPU Mining Rig Machine Motherboard With CPU support 8 GPU PCIE slots USA.
Esonic HM65/HM76 8 slots GPU Mining Motherboard Socket PGA988 ...
Hence why motherboard manufacturers recommend installing the first GPU in the primary slot.