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Performance and PCI Express Bus Lanes

Warning:  Technology changes very quickly so it is always recommended that you look at the date when the article was last updated. If you have any questions feel free to contact us

Date: Wed, 04/18/2018 - 11:22

The amount of PCI Express lanes you have available to you through your PC, largely depends on your CPU and your Chipset. With Intel’s modern chipsets, your CPU largely determines how many PCI lanes you have available to you through your PC.

SKIP TO: Chipset, CPU, and Performance

Why Do PCI-Express Lanes Matter?

Your PCI Express lanes consist of the lanes of communication that your motherboard uses to control your PC's functions. Your CPU, in particular, controls your CPU and memory, as well as those functions that have to do with your primary PCIe slots.

Typical Functions Your CPU's PCIe Lanes Control:

  • CPU Processing
  • Memory
  • Onboard Video
  • PCIe 3.0 x16 Slot (more on some boards)
  • M.2/U.2 (on some Enthusiast Boards)
  • LAN (on some Enthusiast Boards)

Other functions use your CHIPSET's PCIe bus lanes. Older chipsets designate less PCIe 2.0/3.0 lanes for these functions. Functions which your chipset's PCIe lanes control may include:

  • Thunderbolt
  • M.2/U.2
  • SATA hard drives
  • Onboard Sound
  • Onboard RAID
  • Onboard Network Controller
  • PCIe cards plugged into your PCIe x1 slot
  • All PCIe slots except the first one (Socket 1150/1151)
  • Onboard LAN
  • Onboard Sound
  • Sound card
  • Network card
  • RAID controller card

The following are generally accepted amounts of PCIe bandwidth which various components require:

  • 8-16 Lanes - x16 PCIe Video Cards (Each)
  • 8-16 Lanes - FPGA & Other Specialized PCIe Cards
  • 4 Lanes - M.2 Drive
  • 4 Lanes - Thunderbolt (uses 4 lanes PCIe 3.0)
  • 4 Lanes - Hardware Based RAID Controllers
  • 2 Lanes (Each) - SSD Drives
  • 2 Lanes - USB 3.1 (Gen. 2)
  • 1 Lane - USB 3.0 (USB 3.1 Gen. 1)
  • 1 Lane - Sound
  • 1 Lane - Network Controllers

Performance PC Demands

The number of PCIe bus lanes you have available to you can determine the performance of your PC, particularly if you are using performance sensitive software, such as Photo/Video Software, CAD, Financial Software, Audio Production Software, etc. Additionally, if you use your PC for intensive gaming application or to support multiple high-definition monitors, you will have an increased demand placed on your PCIe bus lanes.

If you aren’t using your PC for performance demanding applications, it isn’t likely you need more than 16 lanes of PCIe bus.

However, if you are planning to use your PC for applications that may add up to more than 16 lanes of bus bandwidth, then using Chipsets and CPUs with less PCIe lanes may become a bottleneck for your system, especially during times of intense usage.

Another interesting caveat is that your PC uses DMI (Direct Media Inferface) to communicate between your CPU's PCIe bus lanes and your Chipset's PCIe bus lanes. X99, Z97, and H97 (as well as many previous chipsets) all used DMI 2.0, which is the equivalent of four PCIe 2.0 bus lanes (about 2 GB/s)). Z170/H170 boards used DMI 3.0, which is the equivalent of four PCIe 3.0 bus lanes (about 3.93 GB/s). Current chipsets H270/Z370/B250, as well as X299 (X-Series) and Xeon-W all use DMI 3.0. If you have several chip-side devices communicating to your CPU bus, this may be your bottleneck in your PC.

PCIe 3.0 Effective Speed

When all PCIe bus lanes are being used on a PC, your PC negotiates which device gets how much PCIe bandwidth. Most of the motherboards we use in our systems use the latest version of PCIe (PCIe 3.0). PCIe 3.0 has almost doubled the effective bandwidth (after overhead) of each PCIe bus lane when compared to PCIe 2.0. PCIe 2 had 500 MB/s effective bandwidth. PCIe 3.0 has 985 MB/s effective bandwidth.

If you are using your PC for demanding applications, it is recommended that you choose a system with more available PCIe lanes.

Which Chipset Should I Use?

Intel's X-Series CPUs are Intel’s performance line of CPUs. Overall, these CPUs have more performance potential than Socket 1151 CPUs (Intel's 8th Generation Core Consumer CPUs). However, X-Series CPUs (Socket 2066 i5-i9) are more expensive and they produce more heat (use more power and require more cooling - either by using larger heatsinks or through the use of fans).

The following chart explains the performance, bus lanes, and power usage of various chipsets featured in our PCs, to help you make your decision about which PC is right for you. In our chart, we used Passmark CPUMark rankings from this resource (as of the time of this writing), for your convenience. If you wish to look up your particular CPU's performance please refer to: https://www.cpubenchmark.net/cpu_list.php


 
Chipset Chipset Lanes DMI Socket CPU CPU Lanes CPU Benchmarks CPU Heat
Intel B250 12 PCIe 3.0 Chipset Lanes DMI 3.0 (8 GT/s) Socket 1151 Kaby Lake Celeron G3930 to i7-7700K 16 PCIe 3.0 CPU Lanes 3073 to 12069 51w to 91w
Intel C236 20 PCIe 3.0 Chipset Lanes DMI 3.0 (8 GT/s) Socket 1151 Xeon E3 v6 E3-1220 to E3-1275 16 PCIe 3.0 CPU Lanes 6067 to 11035 65w to 73w
Intel H270 20 PCIe 3.0 Lanes DMI 3.0 (8 GT/s) Socket 1151 Kaby Lake Celeron G3930 to i7-7700K 16 PCIe 3.0 Lanes 3073 to 12069 51w to 91w
AMD X370 8 PCIe 3.0 Lanes NA Socket AM4 Ryzen 5 1600 to Ryzen 7 1800X 24 PCIe 3.0 Lanes
(4 Used To Interface with Chipset)
12383 to 15403 65w to 95w
Intel C236 20 PCIe 3.0 Chipset Lanes DMI 3.0 (8 GT/s) Socket 1151 Xeon E3 v6 E3-1220 to E3-1275 16 PCIe 3.0 CPU Lanes 6067 to 11035 65w to 73w
Intel Z370 24 PCIe 3.0 Lanes DMI 3.0 (8 GT/s) Socket 1151 Coffee Lake Celeron G4900 to i7-8700K 16 PCIe 3.0 Lanes 3040 to 12069 54w to 95w
AMD X399 66 PCIe 3.0 Chipset Lanes NA AMD TR4 Threadripper 1900X to 1950X 64 PCIe 3.0 CPU Lanes 15401 to 22069 180w
Intel X299 24 PCIe 3.0 Chipset Lanes DMI 3.0 (8 GT/s) Socket 2066 Core X-Series i5-7640X to i9-7980XE 16 to 44 PCIe 3.0 CPU Lanes 9375 to 27795 112w to 165w
Intel C422 24 PCIe 3.0 Chipset Lanes DMI 3.0 (8 GT/s) Socket 2066 Xeon-W Workstation CPUs W-2123 to W-2195/td> 48 PCIe 3.0 CPU Lanes 9375 to 27795 120w to 140w
Intel C612 8 PCIe 2.0 Chipset Lanes DMI 2.0 (5 GT/s) Socket 2011v3 Dual Xeon E5-2603 v4 to E5-2699 v4 40 PCIe 3.0 CPU Lanes Each CPU 6311 to 34330 85w-145w Each CPU
Intel C621 20 PCIe 3.0 Chipset Lanes DMI 3.0 (8 GT/s) Socket 3647 (Socket P)
*No Quiet CPU Coolers Available Yet*
*Ask For Custom Quote*
Dual Xeon Bronze 3104 to Dual Xeon Platinum 8153 48 PCIe 3.0 CPU Lanes Each CPU 9410 to 35948 (Gold 6154) 125w-205w Each CPU

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