Same GPU won't work in first PCIe slots in 2 different motherboards?

Many People Put This In The Wrong GPU Slot which gpu slot to use When installing a graphics card, you should typically put it in the topmost PCIe x16 slot on your motherboard This slot offers the best performance and is which slot apps pay real money I couldn't get any signal from the graphics card, only the onboard VGA would work when I plugged into the onboard vga, plugged into the graphics

which slot does washing powder go in If you ever looked at a PCI to PCIe x16 adapter and wondered what'd happen if you were to stick a modern PCIe GPU in it,