[SOLVED] CPU PCIe vs Chipset PCH PCIe

[KHendrickson93]

I'm looking at a motherboard that has 24 pch pcie lanes. If I plug an nvme m.2 ssd through the chipset pch pcie lanes, does that mean it is sharing bandwidth with your keyboard, mouse, sound card, sensors, fan controllers, SATA ports, LAN, Other NVME, etc. where if the NVME is connected directly to the CPU you get the full PCIE3x4 Bandwidth for your drive?

i.e. cpu connected nvme > chipset connected nvme

 

[TechyInAZ]

No chipset pci-e devices only sometimes share lanes between storage devices only. Never usb ports or ethernet ports or audio jacks.

I believe the latest chipsets have PCI-E 3.0 via chipset for NVME. But either way, CPU PCI-E M.2 slots are always the fastest.

 

[Aeacus]

I could be wrong but this is how i know it to be:
With consumer grade CPUs and MoBos, CPU PCI-E lanes are exclusive to the 1st and 2nd PCI-E x16 slot, meaning that any M.2 NVMe drive used will use chipset PCI-E lanes. While some consumer grade MoBos do enable M.2 NVMe drive to use CPU PCI-E lanes, do note that consumer grade CPUs have max 16x PCI-E lanes and M.2 NVMe drive would be sharing PCI-E lanes with GPU.

For MoBo's with 24x PCI-E lanes, look towards any Intel Z370/Z390 or AMD X370/X470 chipset MoBo.

 

[KHendrickson93]

Would anyone happen to know if 2 nvme m.2s share bandwidth?

 

[KHendrickson93]

No chipset pci-e devices only sometimes share lanes between storage devices only. Never usb ports or ethernet ports or audio jacks.

I believe the latest chipsets have PCI-E 3.0 via chipset for NVME. But either way, CPU PCI-E M.2 slots are always the fastest.

By how much? And if I used an nvme m.2 pcie for the operating system and another for everything else, would they share bandwidth and hinder performance?

 

[Aeacus]

M.2 NVMe drives use the chipset PCI-E lanes and don't share bandwidth with each other, instead they share bandwidth with SATA ports. E.g on my Z170A Gaming M5 MoBo, 1st M.2 NVMe SSD doesn't disable any of my 6x SATA ports. But if i were to install 2nd M.2 NVMe drive, 5th and 6th SATA port will be disabled.

 

[KHendrickson93]

M.2 NVMe drives use the chipset PCI-E lanes and don't share bandwidth with each other, instead they share bandwidth with SATA ports. E.g on my Z170A Gaming M5 MoBo, 1st M.2 NVMe SSD doesn't disable any of my 6x SATA ports. But if i were to install 2nd M.2 NVMe drive, 5th and 6th SATA port will be disabled.

I just learned there's something called a PLX chip and it affects the distribution of pcie lanes between the gpu and the nvme m.2.

Can someone please explain this a bit more to me?

 

[Aeacus]

Found this:

The generic term is a PCI Express Switch; PLX is a company that makes these chips. The number of PCI Express lanes is limited by what the CPU provides, there is no way to get around that. A PCIe switch allows more slots on the motherboard to be wired with lanes, maybe with a 16-lane CPU, a switch would allow you to have 32 lanes active at the same time. However, the switch itself is only connected back to the CPU through the 16 lanes that the CPU provides. So the total amount of PCIe bandwidth isn't increased by a PCIe switch. But switches can be used to circumvent lane restrictions; for example NVIDIA SLI requires at least 8 lanes on each GPU for no reason, and a PCIe switch can be used to fool 3 or 4 GPUs into thinking they're all running on x8 slots, even though only 16 lanes are available in total.

Or if you want to know in-depth workings of PCI-E switch, here's an article for you to read,
link: https://www.anandtech.com/show/6170/four-multigpu-z77-boards-from-280350-plx-pex-8747-featuring-gigabyte-asrock-ecs-and-evga