How Many PCIe Lanes Do You Really Need?
PCIe bifurcation settings in PCIe x16 slots with different Ryzen™ CPUs. 3rd/2nd/1st Generation AMD Ryzen™ Processor. 2nd and 1st Gen AMD Ryzen™ with Radeon™ Vega Graphic Processor. 2nd and 1st Gen AMD Athlon™ with Radeon™ Vega Graphics Processors. M.2 SSD quantity. M.2 SSD quantity. M.2 SSD quantity. Actually I have a mohterboard but I dont know how to determine whether it has a x16 lane or not so I have heard that it is the longest lane BUT HOW MUCH, please if you know or have a x16 slot than help me out by telling the lenght in inches, cm, mm etc I am going to buy a ati radeon hd 5850 so I wanted to know wether it will be compatible or not.
With the new line of X570 motherboards coming up, PCIe 4.0 is finally within reach for the average consumer. With that in mind, it seemed like a good idea to talk about PCIe lanes. What are they exactly, and how many lanes do you really need?
First, a refresher: PCIe 3.0 is the current expansion bus standard used on most modern motherboards. It's the hardware interface between devices (e.g., video cards, sound cards, M.2 drives, network cards) and the motherboard. The slots come in various sizes (x1, x2, x4, x8, and x16)1, and the speed of a given slot is determined by the number of available PCIe lanes.
The total number of lanes for a slot are broken up into thesame numbers as above (1, 2, 4, 8, 16). However, to make things slightly
confusing, the number of lanes in a slot does not always match the physical slot length. Meaning, you can (and often do) encounter a x16 slot with only 8 lanes. Pro-tip: you can actually see this by looking for the shiny little contacts in the slot itself. If the contacts only go up halfway, that x16 slot only has 8 lanes.
But 8 lanes are often plenty. Even though the theoretical data transfer limits of 8 and 16 lane slots are vastly different2, there is currently no consumer card on the market capable of saturating the bandwidth of a PCIe 3.0 x16 slot. While the amount of data being 'crunched' by a high-end video card is often above that limit, the majority of calculations related to the device are actually handled by the card's internal processor, and therefore do not need to travel through the bus. Performance differences are mainly dependent on the card itself, and not the theoretical limits of the slot.
Motherboards are designed with various amounts of PCIe lanes, and different processors are designed with support for certain amounts of lanes. Server and enthusiast boards are typically designed with more lanes to provide more expandability, and CPU manufacturers segment their products similarly. For example, the Intel Core i7-9700K supports a maximum of 16 lanes, while the Core i9-9980XE supports a maximum of 44. But bigger is not always better—the processors are simply designed for different environments.
However, to complicate things further, there is such a thing known as a PCI Express Switch, which is a chip on some motherboards that is often said to double the number of lanes, but this is not strictly accurate. While it does not magically create more, it does alter how the CPU manages signals to the slots via signal multiplexing. In short, it changes how data is sent and received from the CPU to the PCIe slots in order to utilize the same number of lanes more dynamically across devices to achieve better performance.
Back to the topic at hand: the number of lanes you need depends on how many PCIe devices you want to use in your system, and how fast you want all those devices to run, though noticeable effects on performance usually only occur in niche configurations. A single GPU runs best with 16 lanes. When installing an additional GPU, be sure to use a x16 slot with 16 lanes, if possible. Conversely, if you are adding a x4 card and only have a x8 slot available, that will work too. All PCIe 3.0 slots are compatible with smaller form factor devices, assuming they physically fit into the slot.
Any time you dive into a technology topic, it's easy to become overwhelmed. Luckily, BOXX has done all the research for you and designed workstations to fit any workflow. The APEXX S3, our flagship workstation, is designed for single-threaded applications that run at peak efficiency with a single high-end GPU. However, if you require that same unmatched overclocked processor (8 cores at 5.1GHz) but require more PCIe lanes, the APEXX Enigma S3 is the perfect option. Or if you need even more space, the APEXX S4 has enough lanes to run four dual-width GPUs.
Those are just a few examples. Regardless of your specific needs, BOXX has a workstation with your workflow in mind. Talk to a BOXX Performance Specialist today to learn more.
1 Technically x32 slots do exist, but they're very rare. South point casino theatre.
2 7,880MB/s and 15,760MB/s, respectively.
Peripheral Component Interconnect (PCI) Express (PCIe) is a scalable Input/Output (I/O) serial bus technology that largely replaced earlier PCI slots on motherboards. It is a port that allows certain internal components to be installed into a computer. In 2004, PCI Express slots began appearing alongside standard slots, starting a gradual transition to the new technology. While some standard PCI slots can still be found on motherboards, many computer users prefer PCI express for graphics cards and other components.
The Purpose of PCI Express
PCIe slots are found on many motherboards, letting computer users install components into them. They allow the motherboard and other software in a computer to access and use devices connected to these slots. While PCIe has been used throughout the first decade of the 21st Century, new slots are likely to replace them at some point in the future.
Benefits of PCIe Technology
PCI Express is a point-to-point connection, which means it does not share bandwidth but communicates directly with devices via a switch that directs data flow. This allows for 'hot swapping' or 'hot plugging,' which means cards in PCIe slots can be changed without shutting down the computer, and they consume less power than previous PCI technology. One of the most promising features of PCIe is that it is scalable, which means greater bandwidth can be achieved through adding more 'lanes.'
PCI Express has several additional advantages, not only to the user but to manufacturers. It can be implemented as a unifying I/O structure for desktops, servers, and workstations, and it is cheaper than PCI standard to implement at the motherboard level. This keeps costs low for the consumer. It is also designed to be compatible with earlier Operating Systems and PCI device drivers.
Types of PCIe Formats
The initial rollout of PCI Express provided three consumer options: x1, x2, and x16. These numbers represents the 'lanes:' x1 has 1 lane; x2 has 2 lanes, and x16 has 16. Each lane is bi-directional and consists of 4 pins. Lanes in PCIe version 1.x had a lower delivery transfer rate, but PCIe 3.0 introduced a transfer rate of 500 megabytes per second (MBps) in each direction for a total of 1,000 MBps, or 1 gigabyte per second (GBps), per lane.
PCIe | Lanes | Pins | MBps | Purpose |
x1 | 1 | 4 | 1 GBps | Device |
x2 | 2 | 8 | 2 GBps | Device |
x16 | 16 | 64 | 16 GBps | Graphics Card |
PCIe and Graphics Cards
The 16-lane (x16) slot has replaced the Accelerated Graphics Port (AGP) on many motherboards and fits a PCIe graphics card. Boards that include the x1 and x2 slots usually have them for other components, such as sound or networking cards. As computer graphics demands increase, x32 and x64 slots may become available, and future versions of PCIe might improve upon lane data rates.
Other PCI Technologies
PCI Express should not be confused with PCI eXtended (PCI-X), used in the server market. PCI-X improved on standard PCI bus to deliver a maximum bandwidth of 1GBps. PCIe has been developed for the server market as well, initially with the x4, x8 and x12 formats reserved. This far exceeds PCI-X capability.
Pcie Lane
History of PCI Technology
Pcie Lanes Explained
Intel first introduced PCI technology in the early 1990s to replace the Industry Standard Architecture (ISA) bus. Although robust enough to last over a decade, total available bandwidth of just 133 MBps, shared between slots, meant that high demand devices quickly overwhelmed computer resources. In 1997 this problem was partially alleviated by implementation of a separate AGP slot with dedicated bandwidth. However, as component manufacturers developed many high-demand devices for computers, a new architecture was required, which led to the introduction of PCI Express.