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The PCI Express (PCIe) standard has been the primary connection interface for expansion cards in computers for years. Its evolution has allowed for an exponential increase in bandwidthBandwidth is the maximum transfer capacity with each generation, facilitating the use of graphics cards, storage devices, sound cards, and other peripherals. This article details the differences between PCIe x1, x4, x8, and x16 modes and analyzes whether they affect the performance of a graphics card.
What is PCI Express?
PCI Express (Peripheral Component Interconnect Express) is a high-speed serial communication interface designed to replace PCI, PCI-X, and AGP buses. Its modular architecture allows for flexible performance scaling through different lane configurations.
Each generation of PCIe approximately doubles the bandwidth of the previous version while maintaining compatibility with earlier versions. Currently, PCIe 5.0 is the dominant standard, while PCIe 6.0 is in the process of implementation.
Types of PCI Express Slots
PCIe uses different slot sizes and numbers of data lanes, which determine its speed and bandwidth. The most common configurations are:
- PCIe x1: A single data lane, used for sound cards, network cards, and video capture cards.
- PCIe x4: Four data lanes, ideal for NVMe storage, RAID cards, and high-speed networking.
- PCIe x8: Eight data lanes, used for mid-range graphics cards and advanced storage adapters.
- PCIe x16: Sixteen data lanes, the maximum available for graphics cards and high-performance devices.
Performance Based on Lane Count
The number of PCIe lanes influences the bandwidth available for communication between the device and the motherboard. Below is a table with the theoretical bandwidth of each generation:
| Configuration | PCIe 1.0 | PCIe 2.0 | PCIe 3.0 | PCIe 4.0 | PCIe 5.0 |
|---|---|---|---|---|---|
| x1 | 250MB/s | 500MB/s | 985MB/s | 1969MB/s | 3938MB/s |
| x4 | 1000MB/s | 2000MB/s | 3940MB/s | 7876MB/s | 15752MB/s |
| x8 | 2000MB/s | 4000MB/s | 7880MB/s | 15752MB/s | 31504MB/s |
| x16 | 4000MB/s | 8000MB/s | 15760MB/s | 31504MB/s | 63008MB/s |
Does It Affect the Performance of Graphics Cards?
Various tests have shown that the impact of PCIe configuration on the performance of a graphics card is minimal in most cases. Gamers Nexus conducted a comparison using an MSI GTX 1080 Gaming X with an Intel i7-5930K processor, analyzing the impact of using a PCIe x16 slot compared to an x8 slot. The results were as follows:
| Game | PCIe x16 | PCIe x8 |
| Metro: Last Light | 96 FPS | 95 FPS |
| Shadow of Mordor | 108 FPS | 107 FPS |
| Call of Duty: Black Ops 3 | 140 FPS | 140 FPS |
| GTA V | 58.3 FPS | 58 FPS |
The performance difference is negligible, suggesting that a graphics card in PCIe x8 performs practically the same as in PCIe x16 in most games.
Impact on Next-Generation Graphics Cards
TechPowerUp conducted tests with the Nvidia RTX 4090 in PCIe 4.0 x8 and x16, observing an average difference of 2%. In games like Elden Ring, the difference increased to 5%, while in Far Cry 6 at 4K, an 8% difference was recorded. This suggests that although bandwidth can be more relevant in high-resolution games, the impact remains minimal for most users.
Conclusion
The number of PCIe lanes directly affects the bandwidth, but it does not always impact the actual performance of connected devices. For graphics cards, moving from x16 to x8 results in imperceptible differences in games, although there may be slight performance losses in professional applications or at 4K resolutions. Ultimately, if assembling a high-end system, it is advisable to opt for PCIe x16 when possible, but in dual GPU configurations or when lane limitations exist, PCIe x8 still offers more than adequate performance.