Intel versus AMD - PCIe lane mix-up Confusion about lanes is common in modern hardware.
Intel versus AMD - PCIe lane mix-up Confusion about lanes is common in modern hardware.
Consider it straightforward. Both consumer platforms offer 16x CPU to PCIe slots. Typically used as a single 16x for a GPU, but the actual configuration can vary based on the motherboard. Chipset lanes reuse bandwidth back to the CPU. On the X570, this is less of an issue since it supports PCIe 4.0. AMD has a slight edge because it also provides 4x off-CPU support for NVMe drives. If you have only one additional card besides the GPU, the choice doesn’t really matter as long as your motherboard includes two 16x slots (operating at 8x when both are active) connected to the CPU. That setup will handle the GPU and the more demanding PCIe card. Adding a third card will draw power from the chipset, so prioritize the lower-performing component. It should still deliver around 4GB/s on Intel and possibly higher on AMD.
Chipset and CPU lanes serve different purposes despite both being PCIe lanes. Chipset lanes come from a chipset with limited overall bandwidth, which is less than the total number of available lanes. For instance, the AMD X570 chipset connects to the CPU using PCIe 4.0 x4, even though it may have around 12 lanes and additional connections. Essentially, a PCIe 4.0 x4 SSD will perform at its peak when used alone but slows significantly if other devices like SATA drives are also active. Regarding CPU lanes, the AMD AM4 Ryzen offers 20 lanes while the Intel LGA 115x provides 16. The remaining four lanes are dedicated to an M.2 slot, enabling support for x4, x2, or SATA connections. Time traveller discovered that technology existed before the 21st century—just slows things down. As long as the board has sufficient working slots (some can be turned off when another is in use), it will function at least partially.
Both AMD and Intel provide a combined total of 16 user-accessible lanes from the CPU, excluding the chipset lanes.
I don't believe that's a significant improvement. It's a minor point overall. Intel's main CPUs provide 16 PCIe lanes, mostly for graphics cards, and also include a 4-lane link to the chipset. AMD Ryzen CPUs offer 16 PCIe lanes for graphics use plus an additional 4 lanes for NVMe drives, with another 4-lane connection to the chipset. Either way, the CPU delivers 4 extra lanes compared to Intel in this scenario.
Unless you're focusing on physically connecting RAM or the GPU, PCIe lanes for the CPU seem unnecessary. I think devices like SAS cards manage all data transfers internally—no need to route anything through PCIe. If information flows from storage to the card and then to RAM or the CPU, someone would have to be manually redirected, which is a hassle.
The processor generates numerous PCI-E lanes. The chipset also establishes many PCI-E lanes. AMD chips without built-in graphics offer 24 PCI-E lanes divided as follows: one set for video cards, another for M.2 connectors, and the remaining always linked to the chipset. Depending on the chipset, these 16 lanes can be organized into two PCI-E x8 slots for SLI or Crossfire configurations with dual cards, though any component can fit in the second slot. Chipsets like x370 and x470 support this setup on AM4 motherboards, while A320, B450, and x570 models cannot split them. For the Ryzen 3xxx lineup, using B450 or x570/x550 is advised. Various PCI-E lanes are available for peripheral devices such as extra SATA controllers or USB ports, or they can extend to additional slots. Generally, a B450 chipset provides six PCI-E 2.0 lanes, whereas x470 and x570 offer eight lanes. On certain boards, adding an NVMe M.2 SSD may block some x1 slots or reduce the x4 slot to just x1. Threadripper models boast a large number of PCI-E connections but come at a higher cost.
You're asking how Intel and AMD handle CPU lanes for different components. Intel depends more on the chipset than the CPU itself, but provides extra lanes—about 16 for graphics and 24 for shared use across four CPUs. AMD offers a higher maximum of 28, but splits them differently: roughly 16 for graphics, 4 for M.2, and 8 for other tasks. This means Intel gives more flexibility in terms of available lanes.
For your setup, since you won’t be using an M.2 drive, the four CPU lanes are likely fixed. If you need extra lanes for PCIe x1 or a SAS card, you’d have to check if your motherboard supports it. The SAS cards you’re considering are external and not RAID-capable, so they’d require pulling data via the PCIe interface. You mentioned you’d prefer AMD because of past security concerns, but you’re open to Intel if you can’t get a compatible SAS card due to PCIe limitations.
In short: 16 lanes for graphics, 24 for shared tasks, and 8 for other uses—depending on your motherboard’s capabilities. The exact numbers depend on your specific hardware.