PCI Express (PCIe) was introduced in 2002 as "Third Generation I/O" (3GIO), and by the mid-2000s, motherboards had at least one PCIe slot for graphics. PCIe superseded PCI and PCI-X. Unlike its ...

PCI and PCI-X are not directly compatible, and you’d be forgiven for thinking that means you’re out of luck if you need to use a PCI-X card in a machine that only has basic PCI slots.

For a while around a quarter century ago PC motherboards came with a special slot, a little shorter than the PCI slots which ruled the roost back then, and offset from them further into the case.