Why Are There 2 PCI Slots?

Most motherboards come with two PCI slots. But why? Is it just to give you the option to add more than one expansion card, or is there some other reason?

The answer is a bit of both. Having two PCI slots gives you more options for expandability and future proofing.

But there’s also another reason.

The first reason is pretty simple. If you want to add more than one expansion card to your computer, you’re going to need more than one PCI slot.

For example, if you want to add a sound card and a wireless network card, you’re going to need two PCI slots.

The second reason is a bit more complicated. It has to do with the way PCI slots are designed.

Each PCI slot has two sets of pins, called bus lanes. One set of bus lanes is used for data transfer and the other set is used for power.

Most expansion cards only need one set of bus lanes (usually the data transfer lanes). But some cards, such as graphics cards, need both sets of bus lanes in order to work properly.

That’s why most graphics cards come with their own power connectors – they need the extra power that the second set of bus lanes provides.

So, if you want to add a graphics card to your computer, you’re going to need two PCI slots: one for the data transfer bus lanes and one for the power bus lanes. That’s why most motherboards come with two PCI slots: to give you the flexibility to add any kind of expansion card you want.

There are some motherboards that come with only one PCI slot, but they’re not very common. If you’re looking at buying a new motherboard and you see one that only has one PCI slot, make sure it’s the right kind of slot for your needs (most likely it will be a PCIe slot).

Or, better yet, just get a motherboard that comes with two PCI slots. It will save you a lot of headaches down the road.