I'm a first time PC builder. I'm looking at mainboards. Some mainboards say they have a "PCIE 4.0 x16 (x4)" connection. I know what PCIE 4.0 x16 is but the (x4) confuses me. (Example mainboard: MSI PRO B760-P WIFI DDR4)

Does that mean that that particular PCIE slot will be x16 in length but can only run at x4 speed? Some mainboards even have PCIE 3.0 x16 (x1) at which point I'm asking myself why even use the manufacturing material to make the slot that long only for it to be able to use x1 speed at max.


1 Answer 1


A PCIe x16 (x4) slot is a PCIe x4 slot, designed so that PCIe x16 card can also be inserted into the slot an work, albeit running at the slower speed of PCIe x4. This type of slots allows more solid state drives, for example, to be inserted than the number of actual optimally-sized connections (x4 for solid state drives) the motherboard or CPU can offer.

This slot in a not-very-common shape explains the concept well:

An open end PCIe x1 slot which allows longer cards using more lanes to be plugged in. Open end slots are less common than slots in a longer form factor due to increased risk of short-circuiting.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .