This is a quick guide on how PCI Express lanes are distributed.   Graphics are always given their own PCI Express lanes No matter what the socket or chipset or processor, PCIe slots meant for graphics cards are always given their own PCI Express lanes. In the older northbridge/southbridge chipset setup, PCI Express lanes meant for the graphics card always went through northbridge, which is the faster chipset. Normally northbridge gave 16 lanes in a x16, x8/x8, x8/x4/x4, or x4/x4/x4/x4 configuration. Higher end chipsets and processors will have more lanes. To summarize in a list: Intel's LGA115x processors 16 lanes configurable in x16, x8/x8, or x8/x4/x4 Intel's HEDT processors Up to 40 lanes. Intel officially says this can either be a x16/x16/x8 or x8/x8/x8/x8/x8 configuration. Lower end processors will only have 28 lanes, which can only be x16 or up to x8/x8/x8. AMD AM3+ and AM4 processors (FX and Ryzen) 16 lanes configurable in x16, x8/x8, or x8/x4/x4 AMD claims that Ryzen processors have 24 PCIe lanes, but 4 lanes are dedicated to the chipset and 4 are for general purpose use. The general purpose use ones tend to be allocated for NVMe storage, but it really depends on the motherboard manufacturer. AMD APUs 4 or 8 lanes are provided for a single GPU configuration Zen based APUs have 4 general purpose lanes AMD Threadripper Up to 60 PCIe lanes. AMD claims there are 64 total, but 4 lanes are dedicated to the chipset. However in some configurations, you may be limited down to 48 PCIe lanes for graphics if you are using NVMe storage. The chipset provides additional PCI Express lanes for other use Any time you see a smaller PCIe slot, like an x1 or x2 slot, they will route to the chipset. So if you see a motherboard with something like "8 PCIe lanes" or "20 PCIe lanes", it's coming from the chipset, not the CPU.   Peripherals all go through the chipset/southbridge's PCIe lanes, not the processors/northbridge's Things like USB ports, SATA, Ethernet, etc. all go through the PCIe lanes that the chipset provides, if the chipset doesn't provide the feature natively.   As a visual aid, this diagram (from https://www.anandtech.com/show/9485/intel-skylake-z170-motherboards-asrock-asus-gigabyte-msi-ecs-evga-supermicro) shows what's available on a Z170. The chipset has 26 "ports", 20 of which can be used as PCIe lanes.   PCIe Lanes are typically distributed in powers of 2 A PCIe controller will only give lanes to a device in powers of 2, or 1, 2, 4, 8, 16 and theoretically 32 (nobody makes a 32 lane expansion device as far as I know). So for example, if there are 16 lanes from the CPU and you plug in a graphics card and then an x1 PCIe card into another graphics card slot, the processor will give the graphics card 8 lanes instead.   Note that while the official PCIe specification allows for a 4 + 12 lane combination in a 16 lane configuration, almost nobody uses this setup   Pay attention to what NVMe does to your system NVMe requires PCIe lanes; where it gets them from depends on the platform you go with. Intel's mainstream boards (LGA115x) These take lanes from the chipset. This may disable other I/O like a PCIe slot or a couple of SATA ports Intel's HEDT boards (LGA 20xx) These primarily take lanes from the CPU AMD prior to AM4 These take lanes from the Southbridge AMD mainstream boards (AM4) All processors have 4 lanes dedicated for general use. This tends to be wired for NVMe storage, but it depends on the motherboard. If there is more than one M.2 slot for NVMe use, the other ones will use lanes from the chipset similar to Intel's mainstream boards. AMD HEDT These primarily take lanes from the CPU.   In short Just remember the first point: For most users, the graphics cards are always given their own PCI Express lanes. However, even if some peripherals were using up the lanes meant for graphics, graphics cards can run just fine down to PCIe 3.0 x4 without much performance loss.   If you're using an HEDT platform, NVMe storage may eat into the PCIe lane budget, but unless you're rocking 3 cards or are using a lower end HEDT processor, this won't be a problem to worry about.