PCIe is a physical interface for connecting high speed devices such as graphics cards, network cards, storage adapters and capture device to a desktop PC.
This is not an exhaustive article on PCIe. This article will give a base understanding to help ensure that you know which slots and configurations of PCIe devices your PC will support.
To learn more about PCIe, head over to https://en.wikipedia.org/wiki/PCI_Express.
Table of contents
- What does PCIe stand for?
- PCIe Generation
- PCIe Slot Size / Lane Width
- How to identify PCIe slot size
- How to read PCIe specifications
- Elgato PCIe Product Specifications
- Example setups with Elgato capture devices
- PCIe and M.2
What does PCIe stand for?
PCIe is short Peripheral Component Interconnect Express.
PCIe has various different specifications.
The PCIe generation refers to updated standards, enabling faster speeds. PCIe generations are denoted as PCIe 2.0, PCIe 3.0, and PCIe 4.0. As of the writing of this article, PCIe 4.0 is the latest generation.
Like USB, PCIe is forward compatible. This means that a device which requires PCIe 2.0 will work in a PCIe 3.0 or PCIe 4.0 slot.
Slot Size / Lane Width
Slot Size refers to the size of the physical PCIe slot.
Lane Width refers to the number of PCIe lanes supported by the physical slot. Larger slots can support more lanes, enabling higher speeds. But not all devices will use all of the lanes provided by a slot.
The smallest PCIe slot will run at x1 speed, while a full-size PCIe slot will run at x16.
PCIe x16 slots are generally intended for use with Graphics Cards. PCIe 1x slots are generally for smaller add-in cards like Wifi Adapters, USB Adapters, or lower bandwidth capture devices such as HD60 Pro.
Like USB, PCIe is forward compatible. This means that a device which requires slot size x4 will work in slot size x8 or slot size x16 lane.
Note: On some motherboards, a PCIe slot might physically be a full-sized x16 slot to support a full-sized device but only have the pins to electrically connect two, four, or eight lanes. Check with your motherboard's manual or motherboard manufacturer to make sure it supports the proper lane width for the PCIe device.
How to identify size of PCIe slot
The image below shows the four types of PCIe slot sizes which are part of the PCIe specification.
How to read PCIe specifications
The graphic below shows how to a PCIe specification when written out.
Elgato PCIe Product Specifications
These are the PCIe specifications of Elgato's PCIe products.
- PCIe 2.0 x1
- PCIe 2.0 x4
Cam Link Pro
- PCIe 2.0 x4
Examples with Elgato capture devices
Elgato has various PCIe devices.
Game Capture HD60 Pro is a PCIe 2.0 x1 device.
Game Capture 4K60 Pro MK.2 is a PCIe 2.0 x4 device.
Game Capture HD60 Pro
In this example, HD60 Pro works in any slot, as it requires a minimum of x1 slot size and speed.
Game Capture 4K60 Pro
In this example, 4K60 Pro does not work in the x1 slot due to the size of the slot, as well as the required speed.
Game Capture 4K60 Pro MK.2
In this example, a M.2 SSD is installed and the PCIe x4 slot has been disabled due to motherboard restrictions. 4K60 Pro will not work in the x4 slot. It can still be used in the available x8 and x16 slot.
Game Capture 4K60 Pro MK.2
In this example, another PCIe device is installed, using up more PCIe lanes. Due to the motherboard layout, the speed of the x4 lane is reduced to x1. 4K60 Pro can still be installed in this slot, however it will not function correctly due to the reduced speed.
PCIe and M.2
M.2 is a interface standard based on PCIe. PCIe and M.2 share the same available bandwidth.
Motherboard manufacturers have a limited amount of PCIe lanes available to them based on the chipset and CPU being used. They determine how many PCIe slots and M.2 slots will be on the motherboard and which speed those slots run at.
Some motherboard manufacturers will add more PCIe slots and M.2 slots than PCIe lanes are available. This means that when a M.2 SSD is being used, a PCIe slot may be disabled. Or in reverse, when a PCIe slot is used, the M.2 interface is disabled. The same can happen with SATA or eSATA ports.
In this example with the MSI B550M Mortar motherboard, when a M.2 SSD is installed, the PCIe x4 slot will be disabled.
Also note how the specification suggests it is a full-size PCIe 3.0 x16 slot, however it only supports up to x4 speed.
Please refer to your motherboard manual to find out which combination of interfaces can work at the same time.