- Post Publish: 2023-04-24
- Categories: Knowledge
- Updated:
- Posts by Mina Xiao
What is PCIe(Peripheral Component Interconnect Express)?
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PCIe (peripheral component interconnect express) is an interface standard for connecting high-speed components. Every desktop PC motherboard has a number of PCIe slots you can use to add GPUs(aka video cards aka graphics cards), RAID cards, Wi-Fi cards, or SSD(solid-state drive) add-on cards.
The types of PCIe slots available in your PC will depend on the motherboard you buy. In addition to standard motherboard components, computers often need to be equipped with other parts and components to achieve the desired functionality.
In this blog, you’ll learn more about what PCIe is, its different components, and how it helps enhance a computer’s capabilities to maximize efficiency at the edge.
What Is PCIe?
PCIe stands for Peripheral Component Interconnect Express, often abbreviated as PCI-e, PCIe, or PCI Express; all are the same. PCI Express is a popular high-speed serial computer expansion bus standard that supersedes other legacy standards such as PCI, PCI-X, and AGP.
Compared to PCI, which applies parallel communication, PCIe uses a serial link connection architecture that utilizes a point-to-point topology, which makes PCIe more reliable, faster overall, and less expensive to produce than the PCI bus. Therefore, most motherboards and computers today are configured with PCI-e slots for expandability capabilities.
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How do PCIe slots work?
PCIe slots come in different physical configurations: x1, x4, x8, and x16. The number after x tells you how many lanes the PCIe slot has.
For example, a PCIe x1 slot has one lane and can move data at one bit per cycle. A PCIe x2 slot has two lanes and can move data at two bits per cycle.
Let’s take a look at the different types of slots:
1. PCIe x1: The length of the slot is the shortest, only 25mm. The motherboard chip usually provides the bandwidth of the PCI-E x1 slot. It is mainly used for independent network cards, independent sound cards, USB 3.0/3.1 expansion cards, etc. to the PCI-E x1 slot.
2. PCIe x4: The length of the PCI-E x4 slot is 39mm, which is also realized by reducing the data pins based on the PCI-E x16 slot. However, like the PCI-E x8 slot, most PCI-E x4 slots are now in the form of PCI-E x16 or x8 slots or expanded to M.2 interfaces for compatibility. Often used for single M.2 NVMe SSD expansion cards, they are also used for SATA 3 expansion cards and high-speed network adapters.
3. PCIe x8: The x8 slot is 56mm long and has 98 pins. For compatibility, some PCI-E x8 slots are processed into the form of PCI-E x16 slots, but only half of the data pins are valid. That is to say; the actual bandwidth is only half that of a real PCI-E x16 slot. Most commonly used for GPUs or for M.2 NVMe SSD expansion cards.
4. PCIe x16: The x16 slot is 89mm in length, has 164 pins, and has a bayonet outside the motherboard. The slot has excellent compatibility and can be backward compatible with x1/x4/x8 level devices, which is the universal slot of PCI-E.
By far, the most popular setup is PCIe x16, as most GPUs require it to operate at its full potential.
There are two components to a PCIe slot: mechanical (cards) and electrical (lanes).
For instance, you can have a slot that is x16 mechanical that is x8 electrical, meaning that you can house 16 cards, but it can only support 8 lanes which may lead to lower performance.
Additionally, you can insert x8 mechanical into an x8 mechanical and x4 electrical for half the performance.
PCIe Generations Compared
| Bandwidth | Gigatransfer | Frequency | |
|---|---|---|---|
| PCIe 1.0 | 8 GB/s | 2.5 GT/s | 2.5 GHz |
| PCIe 2.0 | 16 GB/s | 5 GT/s | 5 GHz |
| PCIe 3.0 | 32 GB/s | 8 GT/s | 8 GHz |
| PCIe 4.0 | 64 GB/s | 16 GT/s | 16 GHz |
| PCIe 5.0 | 128 GB/s | 32 GT/s | 32 GHz |
| PCIe 6.0 | 256 GB/s | 64 GT/s | 32 GHz |
What Is PCIe Used for?
The purpose of using PCIe is to achieve significantly improved system throughput, scalability, and flexibility at a lower cost.
Due to its robust scalability, PCIe supports devices including embedded industrial display, graphics cards, solid-state drives (PCIe interface), wireless network cards, wired network cards, sound cards, video capture cards, PCIe to M.2 interface, PCIe to USB interface, PCIe Transfer Type-C interface, etc.
PCIe not only has a high transfer rate but is also good in compatibility. It is compatible with PCI at the software level, version upgrade, backward compatible with PCI software, and supports hot plugs.
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