> So in theory one could install a GPU or HBA in one of those x1 slots on the motherboard if one isn't terribly concerned about bandwidth. Except most of the mo

> So in theory one could install a GPU or HBA in one of those x1 slots on the motherboard if one isn't terribly concerned about bandwidth. Except most of the motherboards use x1 connectors which doesn't have an "open back" for larger cards... so much for that[1]. It's not so simple, there's another factor other than the number of lanes: power. According to Wikipedia (https://en.wikipedia.org/wiki/PCI_Express#Power https://en.wikipedia.org/wiki/PCI_Express#Power), a x1 slot is limited to 25W on the 12V pins, while a x16 slow has a higher limit of 66W; the power pins are the same, but the maximum current is higher (2.1A vs 5.5A).