PCI-Express: What Is PCIe?

What Is PCI-Express?

PCI-Express (PCIe) is an electrical bus used in nearly all modern consumer and server PCs. PCIe slots on desktop PCs allow for connecting various expansion boards, including graphics cards, sound cards, video capture cards, network/Wi-Fi cards, storage devices, and more. PCI-Express is the successor of PCI.

PCI-Express is currently the dominant bus for connecting expansion cards and devices (alongside USB, which is used for externally connected devices).

While you may recognize PCI-Express as the name used for the motherboard's expansion ports, the same bus is also used for computer storage interfaces. When PCI-Express is used for storage, the NVM Express (NVMe) storage protocol is typically used. In addition to PCIe slots, motherboards provide a high-speed PCIe connection to devices via connectors such as M.2 and U.2.

Learn more about storage types in Storage Type Comparison: M.2, U.2, NVMe, SATA, SSDs, HDDs

PCIe Slots on a Motherboard Eric Kilby

What Are PCI-Express Lanes?

PCIe lanes are connections between a PCI-Express expansion card or device and the CPU. PCIe lanes often communicate with the CPU via chipsets on the motherboard. Each PCIe lane is composed of 4 wires (two differential pairs).

With naming similar to a road, the number of lanes is referred to as the lane size, or how many lanes wide a link or port uses. A single lane is referred to as x1 or "one lane wide."

The maximum throughput (speed) is multiplied by the number of lanes. An x8 PCIe port has twice the throughput of an x4 port.

Some CPUs and motherboards provide PCI-Express lanes at multiple PCIe versions. In these cases, you can choose which devices need the most bandwidth to decide which should be connected to the highest version PCIe lanes. While laying out your system, keep in mind that PCIe speeds will be based on the lowest PCIe version between the slot/port and the device.

You can insert a PCIe add-in card (AIC) into a slot that supports a higher number of lanes. In this case, it would use up to the number of PCIe lanes that the card has. For example, you could insert an x4 PCIe network card into an x16 PCIe AIC slot, and it would run at full x4 speed.

In various scenarios, a PCIe device may not use the maximum number of lanes for which the device was designed. For example, some motherboards have x8 PCIe ports that are only electrically wired for x4 lanes. In another case, a system may have limited lanes provided by the CPU, distributed based on availability or configuration.

Devices will negotiate the number of lanes to use, based on system availability, and should still perform fine at a reduced overall bandwidth in most cases. Refer to your motherboard's documentation and CPU specifications to determine PCIe lane quantities and allocations.

How Fast Is PCI-Express?

Each generation of PCI-Express roughly doubles the speed. The bandwidth for each PCIe 5.0 lane is 4 GB/s. 4 GB/s per lane means that if you use a PCI-Express 5.0 x16 device, it would have up to 63 GB/s of bandwidth available to it, compared to 32 GB/s for PCIe 4.0.

What Is the Latest Version of PCI-Express?

The latest available version of PCI-Express is PCIe 5.0. PCIe 5.0 CPUs are available from Intel and AMD.

Intel's 12th, 13th, and 14th generation Core CPUs provide PCIe 5.0 support for CPU lanes (i.e., one x16 or two x8 PCIe 5.0 slots) and PCIe 4.0/3.0 speeds for the remaining lanes.

AMD's Zen 4-based Ryzen 7000 desktop CPUs were their first to support PCIe 5.0.

PCIe versions such as 3.0, 4.0, and 5.0 are sometimes informally referred to as PCIe Gen 3, PCIe Gen 4, and PCIe Gen 5. This naming is based on them being the third, fourth, and fifth generations of PCI-Express.

Our Recommended PCIe 5.0 CPUs and Motherboards

• Our recommended Intel 13th gen high-performance enthusiast CPU:
  • Up to 5.8 GHz max-turbo stock speed: perfect for games, video editing, and high-intensity tasks.
  • 24 cores (8 Performance + 16 Efficiency): This combination makes it a great all-around system that can handle any task you throw at it.
  • Virtualization features make it great for running virtual machines.
  • Check the latest price of the Intel Core i9-13900K on Amazon
  • For the Intel Core i9-13900K CPU, you'll need a motherboard with overclocking support to overclock the CPU. Motherboards with the Z790 chipset typically support CPU overclocking. Otherwise, you can use a motherboard with Intel's other 600-series desktop chipsets (e.g., Z690, H670, B660, H610).
• Our recommended motherboard to pair with the i9-13900K:
  • PCIe 5.0 support
  • It supports up to 128 GB of DDR5 memory (DDR5 provides the fastest memory speeds)!
  • 2.5 Gbps Ethernet port is faster than any home Internet speed available with tons of room to spare for file transfers.
  • Wi-Fi 6E makes it easy to reach the fastest speeds and future-proof your Wi-Fi system.
  • Bluetooth 5.3 is great for streaming music to Bluetooth headphones.
  • Five x4 NVMe M.2 slots, which is fantastic! One of these supports PCIe 5.0 speeds, and the rest run at PCIe 4.0 speeds.
  • USB 3.2 Gen 2x2 offers 20 Gbps USB speeds!
  • Check the latest price of the MSI MEG Z790 ACE Gaming Motherboard on Amazon

• Our recommended Intel 13th gen high-performance CPU:
  • Up to 5.4 GHz max-turbo stock speed: perfect for games, video editing, and high-intensity tasks.
  • 16 cores (8 Performance + 8 Efficiency): This combination makes it a great all-around system that can handle almost any task.
  • Virtualization features make it great for running virtual machines.
  • Check the latest price of the Intel Core i7-13700K on Amazon
  • For the Intel Core i7-13700K CPU, you'll need a motherboard with overclocking support to overclock the CPU. Motherboards with the Z790 chipset typically support CPU overclocking. Otherwise, you can use a motherboard with Intel's other 600-series desktop chipsets (e.g., Z690, H670, B660, H610).
• Our recommended motherboard to pair with the i7-13700K:
  • PCIe 5.0 support
  • It supports up to 128 GB of DDR5 memory (DDR5 provides the fastest memory speeds)!
  • 2.5 Gbps Ethernet port is faster than any home Internet speed available with tons of room to spare for file transfers.
  • Wi-Fi 6E makes it easy to reach the fastest speeds and future-proof your Wi-Fi system.
  • Bluetooth 5.3 is great for streaming music to Bluetooth headphones.
  • Five x4 NVMe M.2 slots, which is fantastic! One of these supports PCIe 5.0 speeds, and the rest run at PCIe 4.0 speeds.
  • USB 3.2 Gen 2x2 offers 20 Gbps USB speeds!
  • Check the latest price of the ASUS ROG Strix Z790-E Gaming WiFi 6E on Amazon

• Our recommended Intel 13th gen best value CPU:
  • Up to 5.1 GHz max-turbo stock speed: great for games, video editing, and high-intensity tasks.
  • 14 cores (6 Performance + 8 Efficiency): This combination makes it a great all-around system that can handle almost any task.
  • Virtualization features make it great for running virtual machines.
  • Check the latest price of the Intel Core i5-13600K on Amazon
• Our recommended Value motherboard to pair with the i5-13600K:
  • PCIe 5.0 support
  • It supports up to 128 GB of DDR4 memory.
  • 2.5 Gbps Ethernet port is faster than any home Internet speed available with tons of room to spare for file transfers.
  • Wi-Fi 6E makes it easy to reach the fastest speeds and future-proof your Wi-Fi system.
  • Bluetooth 5.3 is great for streaming music to Bluetooth headphones.
  • Three x4 NVMe M.2 slots, which is fantastic! These slots all support PCIe 4.0 speeds.
  • USB 3.2 Gen 2x2 offers 20 Gbps USB speeds!
  • Check the latest price of the MSI MAG B760 Tomahawk WiFi DDR4 on Amazon

• Our recommended Intel 12th gen high-performance enthusiast CPU:
  • Up to 5.2 GHz: perfect for games, video editing, and high-intensity tasks.
  • 16 cores (8 Performance + 8 Efficiency): Quite a few cores considering the frequency! This combination makes it a great all-around system that can handle almost any task.
  • Virtualization features make it great for running virtual machines.
  • Check the latest price of the Intel Core i9-12900K on Amazon
  • For the Intel Core i9-12900K CPU, you'll need a motherboard with overclocking support to overclock the CPU. Motherboards with the Z690 chipset typically support CPU overclocking. Otherwise, you can use a motherboard with Intel's other 600-series desktop chipsets (e.g., H670, B660, H610).
• Our recommended motherboard to pair with the i9-12900K:
  • PCIe 5.0 support
  • It supports up to 128 GB of DDR5 memory (DDR5 provides the fastest memory speeds)!
  • 10 Gbps Ethernet port is faster than any home Internet speed available with tons of room to spare for file transfers.
  • Wi-Fi 6E makes it easy to reach the fastest speeds and future-proof your Wi-Fi system.
  • Bluetooth 5.2 is great for streaming music to Bluetooth headphones.
  • Four x4 NVMe M.2 slots, which is fantastic! Three of these run at PCIe 4.0 speeds, and one at PCIe 3.0 speeds.
  • USB 3.2 Gen 2x2 offers 20 Gbps USB speeds!
  • Check the latest price of the GIGABYTE Z690 AORUS Master on Amazon

• Our recommended Intel 12th gen value CPU:
  • Less than half the price of the i9-12900K, but still excellent performance at up to 4.9 GHz.
  • 10 cores (6 Performance + 4 Efficiency): This core count makes it suitable for everyday multi-threading tasks, such as having tons of browser windows open.
  • Virtualization features make it great for running virtual machines.
  • Check the latest price of the Intel Core i5-12600K on Amazon
  • For the Intel Core i5-12600K CPU, you'll need a motherboard with overclocking support to overclock the CPU. Motherboards with the Z690 chipset typically support CPU overclocking. Otherwise, you can use a motherboard with Intel's other 600-series desktop chipsets (e.g., H670, B660, H610).
• Our recommended motherboard to pair with the i5-12600K:
  • PCIe 5.0 support
  • It supports up to 128 GB of DDR5 memory!
  • Three NVMe M.2 slots, which is excellent! These all run at PCIe 4.0 speeds.
  • 2.5 Gb Ethernet port is faster than most home Internet speeds with room to spare for file transfers.
  • USB 3.2 Gen 2x2 offers 20 Gbps USB speeds!
  • Check the latest price of the GIGABYTE Z690 AORUS PRO on Amazon

Learn More About PCI-Express

Want to brush up on the latest PCIe products, versions, and features? Check out the articles in this PCI-Express series:

• What is PCIe?, What is PCIe 5.0?, and What is PCIe 4.0?
• Is PCIe 5.0 Worth It? and Is PCIe 4.0 Worth It?
• Which Intel and AMD CPUs Support PCIe 5.0?
• Which Intel and AMD CPUs Support PCIe 4.0?
• Which Motherboards Support PCIe 5.0?
• Which Graphics Cards Support PCIe 4.0?
• How Fast is PCIe 5.0? and How Fast is PCIe 4.0?
• Is PCIe Backward Compatible?
• Can I Put a PCIe x4 or x8 Card in an x16 Slot?
• Can I Use a PCIe 4.0 NVMe SSD in a PCIe 3.0 Motherboard Slot?
• Can I Use a PCIe 3.0 NVMe SSD in a PCIe 4.0 Motherboard Slot?
• Can I Use a PCIe 4.0 Graphics Card in a PCIe 3.0 Slot?
• Can I Use a PCIe 3.0 Graphics Card in a PCIe 4.0 Slot?
• What is the Latest Version of PCIe?
• PCI vs. AGP vs. PCIe? Time to Upgrade!