PCI Express Comparison
What is PCI Express, and what does it stand for?
PCI Express stands for Peripheral Component Interconnect Express and represents a standard interface for connecting peripheral hardware to the motherboard on a computer. In other words, PCI Express, or PCIe abbreviated, is an interface that connects internal expansion cards such as graphics cards, sound cards, Ethernet and Wi-Fi adapters to the motherboard. Furthermore, PCI Express is also used to connect some types of solid-state drives that are usually very fast.
What types of PCI Express slots and sizes are there, and what to PCIe lanes mean?
To interconnect the expansion cards to the motherboard, PCI Express uses physical slots. The common PCI Express slots we see on motherboards are PCIe x1, PCIe x4, PCIe x8, and PCIe x16. The number that comes after the “x” letter tell us the physical dimensions of the PCI Express slot, which, in its turn, is determined by the number of pins on it. The higher the number, the longer the PCIe slot and the more pins that interconnect the expansion card to the slot.
Furthermore, the “x” number also tells you how many lanes are available in that expansion slot. Here’s how the commonly used PCIe slots compare:
● PCIe x1: has 1 lane, 18 pins, and 25 mm in length
● PCIe x4: has 4 lanes, 32 pins, and 39 mm in length
● PCIe x8: has 8 lanes, 49 pins, and 56 mm in length
● PCIe x16: has 16 lanes, 82 pins, and 89 mm in length
PCI Express Slots | Number of Lanes | Pins | Physical Length (mm) |
PCIe x1 | 1 | 18 | 25 |
PCIe x4 | 4 | 32 | 39 |
PCIe x8 | 8 | 49 | 56 |
PCIe x16 | 16 | 82 | 89 |
PCI Express lanes are paths between the motherboard chipset and PCIe slots or other devices that are part of the motherboard, such as the processor socket, M.2 SSD slots, network adapters, SATA controllers, or USB controllers.
In PCI Express, each lane is individual, meaning that it cannot be shared between different devices. For example, if your graphics card is connected to a PCIe x16 slot, it means that it has 16 independent lanes dedicated just to it. No other component can use those lanes except the graphics card.
Here’s an idea that might make it easier for you to grasp what PCI Express lanes are: just imagine that PCI Express is a highway and the cars that drive on it are the data that’s being transferred. The more lanes you have available on a highway, the more cars that can drive on it; the more PCIe lanes you have, the more data that can be transferred.
A PCI Express card can fit and work on any PCIe slot available on the motherboard, as long as that slot is not smaller than the expansion card. For example, you can fit a PCIe x1 card in a PCIe x16 slot. However, you can’t do the opposite. You can mount, for instance, a PCIe x1 sound card in a PCIe x16 slot, but you cannot mount a PCIe x16 graphics card in a PCIe x1 slot.
What PCI Express versions are there, and what data transfer speeds (bandwidth) do they support?
There are four versions of PCI Express in use today: PCI Express 1.0, PCI Express 2.0, PCI Express 3.0, and PCI Express 4.0. Each PCIe version supports roughly double the bandwidth of the previous PCIe. Here’s what each of them offers:
● PCI Express 1.0: has a bandwidth of 250 MB/s per lane
● PCI Express 2.0: has a bandwidth of 500 MB/s per lane
● PCI Express 3.0: has a bandwidth of 984.6 MB/s per lane
● PCI Express 4.0: has a bandwidth of 1969 MB/s per lane
Remember that PCIe slots can offer not just one, but more lanes? The bandwidth values we shared are multiplied by the number of lanes available on a PCIe slot. If you want to calculate how much bandwidth is available for a certain expansion card, you have to multiply its PCIe bandwidth per lane with the number of lanes that are available for it.
For example, a graphics card that supports PCI Express 4.0 and is connected to a PCIe x16 slot has access to a total bandwidth of about 31.51 GB/s. That’s the result of multiplying 1969 MB/s by 16 (PCIe bandwidth per lane * 16 lanes). Impressive, right?
Here’s how PCI Express versions scale when you take PCI Express lanes into account:
PCI Express Version | Bandwidth x1 | Bandwidth x4 | Bandwidth x8 | Bandwidth x16 |
PCIe 1.0 | 250 MB/s | 1.00 GB/s | 2.00 GB/s | 4.00 GB/s |
PCIe 2.0 | 500 MB/s | 2.00 GB/s | 4.00 GB/s | 8.00 GB/s |
PCIe 3.0 | 984.6 MB/s | 3.94 GB/s | 7.88 GB/s | 15.75 GB/s |
PCIe 4.0 | 1969 MB/s | 7.88 GB/s | 15.75 GB/s | 31.51 GB/s |
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