What are PCIe Lanes and Why Do They Matter?

In our last blog post, we discussed the PCI-Express Bus and how it’s going to be releasing PCIe 4.0. However, before then let me talk about the importance of PCIe lanes themselves so you know what you’re getting in to when upgrading or purchasing new computer hardware.

What are PCIe lanes?

Without going too deep into technical detail, PCIe lanes are how things (PCIe devices) on the PCIe bus can talk to the motherboard. It functions similarly to a highway – high traffic needs wider lanes, right? Certain components need higher data transfer rates – more PCIe lanes – so they can keep up with all that heavy usage. You might see them called out as lane width but you’ll usually hear people say by n, like for example x4 or x8.

How many PCIe lanes do I need?

An average computer system requires anywhere from 12-24 lanes of PCI Express bandwidth to operate correctly, depending on the type of card used. Graphics cards usually need 16x while less demanding devices such as USB can run well with 1×1 lane. You should also note that this number will change if you’re using multiple GPUs in SLI or CrossFire configurations. When choosing your hardware, always do a little research about how many lanes each component needs and then add them all together for an accurate estimation of what kind of motherboard (i.e. ATX) you’ll need.

Component Lanes
NVIDIA Graphics 16
AMD Graphics 16
PCIe Storage (Intel 905p, Samsung 970 Pro, etc) 4
RAID cards 4 to 8
USB cards 1
802.11 Wifi 1

How many PCIe lanes with common processors

There are many different numbers of PCIe slots and types depending on the motherboard. These changes happen because some motherboards come with different processors or chipsets. You should know how many PCI Express lanes there are before you start building your computer so that it can hold everything well.

Intel   AMD
Processor PCIe Lanes   Processor PCIe Lanes
Intel Core i5 8600k 16   AMD Ryzen 7 2600X 20
Intel Core i7 8700 16   AMD Ryzen 7 2700X 20
Intel Core i7 8700k 16   AMD Ryzen 7 2700 20
Intel Core i5 9600k 16   AMD Ryzen 7 2600 20
Intel Core i7 9700k 16   AMD Threadripper 1900X 64
Intel Core i9 9900k 16   AMD Threadripper 1920X 64
Intel Core i7 9800X 44   AMD Threadripper 1950X 64
Intel Core i9 9900X 44   AMD Threadripper 2920X 64
Intel Core i9 9920X 44   AMD Threadripper 2950X 64
Intel Core i9 9940X 44   AMD Threadripper 2970X 64
Intel Core i9 9960X 44   AMD Threadripper 2990WX 64
Intel Core i9 9800X 44  

What if I run out of PCIe Lanes?

You’ve done your research and after tallying up how many lanes you think would be best for your needs, unfortunately, some configurations do not allow this. If we were going back to our highway analogy, having too many cars using only one lane would cause a traffic jam – the same goes for computers. However, just because one part of the computer isn’t able to work at its maximum potential, doesn’t mean it can’t keep up; most graphics cards can handle 8 lanes while running efficiently with 16 instead. Despite this downgrade happening in the background, if there aren’t enough lanes available; there will still be a noticeable drop in performance, which may make things difficult depending on what you’re trying to accomplish.

 

Leave a Comment