Your high-speed PCIe card might only be using half the PCIe lanes than it's capable of ...
PC components have a finite number of channels that connect with the CPU. These channels are physically built into the CPU, the motherboard, and the components themselves — and they're called PCIe ...
Be honest, when was the last time you installed anything in a PCIe slot that wasn't a graphics card? We still indulge in this charade, where ATX motherboards come equipped with several 1x and 4x slots ...