PCIe/PCI-E/PCI Express: An Overview in 60 Seconds

What are PCIe/PCI-E/PCI Express?

Definition Of PCIe/PCI-E/PCI Express

Peripheral Component Interconnect Express is the abbreviation for PCIe. It refers to the connection between the motherboard – or host – of a computer and peripherals – or endpoints – such as graphics cards, sound cards, and expansion cards. To link them, insert the PCIe card into the board’s PCIe slot.

4 Common PCIe Slots and Card Types

PCIe slots and cards are classified into four types: x1, x4, x8, and x16. The numbers indicate the card’s or slot’s lane count. Similar to the lanes on a highway, these lanes serve as paths for data to move. For example, x1 has a single lane, X4 has four lanes, and so on. Thus, the more lanes, the more data that may pass across them, and thus the higher the possible data transmission rate.

As implied by the title, the number following the x denotes the physical size of the PCIe card or slot, ranging from x16 to x1.

PCIe Size Comparison Table

Width Pins Length

PCI Express x1 18 25 mm

PCI Express x4 32 39 mm

PCI Express x8 49 56 mm

PCI Express x16 82 89 mm

PCIe Generations – What Are They?

A brief word on PCIe generations. This standard has been established in five iterations. The main distinction between them is that the data transfer rate in each lane has doubled with each subsequent generation. The most recent generation is 4.0, which supports up to 16 gigabits per second per lane. Generation 5.0 products are projected to begin shipping in 2022.

Any number following PCIe on a product or motherboard indicates the compatible version of the PCI Express specification.

PCIe Link Performance Comparison Table

Version Bandwidth (per lane) Bandwidth (per lane in an x16 slot)

PCI Express 1.0 2 Gbit/s (250 MB/s) 32 Gbit/s (4000 MB/s)

PCI Express 2.0 4 Gbit/s (500 MB/s) 64 Gbit/s (8000 MB/s)

PCI Express 3.0 7.877 Gbit/s (984.625 MB/s) 126.032 Gbit/s (15754 MB/s)

PCI Express 4.0 15.752 Gbit/s (1969 MB/s) 252.032 Gbit/s (31504 MB/s)

All PCI Express versions are backward and forward compatible, which means that regardless of the version supported by the PCIe card or motherboard, they should work together at a minimal level.

As you can see, each major update to the PCIe standard has improved the available bandwidth, significantly expanding the linked gear’s capability.

Version enhancements also addressed problems, introduced features, and improved power management, but the most significant change between versions is increased bandwidth.

What Additional PCIe-related Questions Do You Have?