I'm currently choosing parts for a new computer, with my main focus on high PCI Express speed and a large number of slots. In this iteration, I will probably choose a board with an Intel Z97 chipset. The specification says that the Z97 chipset provides a total of 16 lanes Gen3 in 16 lanes, 8/8, or 8/4/4 configurations and 8 lanes Gen2. The mainboard, however, boasts with 4 PCIe slots, configurable with 16/16, 16/8/8 and 8/8/8/8 Gen 3 lanes. I suspect that these four ports are theoretically electrically capable of Gen3 but some of them will just use Gen2. But how can it provide more lanes than the chipset actually supports? Do boards have some kind of PCIe switch that distributes the available bandwidth on the lanes as-needed, capping the total bandwidth to that of 16 lanes, instead of 32, when in high load conditions?
How can mainboards provide more PCIe lanes than the chipset
motherboardpci-expressperformance
Related Solutions
Yes, you are right, but remember: PCIe gen4 x4 is 8GB/s. It is very, very difficult, to saturate this, even with 2 SSDs. Most SSDs are much slower. Like reading with 3.5GB/s is fast, but that would be 7 of 8GB/s. Still 1GB/s left for USB3 - wich usually is much more than enought. This would saturate at least 5 modern HDDs at the same time. Or almost 2 SATA 3 SSDs.
Don't be affraid of that. PCIe also is much less CPU intensive than SATA - this all contributes to much better real life performance. You will not notice a bottleneck. You could in theory reach it, but it is very, very unrealistic in reality. :D
Have fun with your nice Setup.
I have a AMD RX 5700XT GPU paired with a Ryzen 2700x CPU, and have been having a ton black screen crashing while gaming. My computer stays on, sound stays on, but both my screens turn black. There's no way out of it other than a hard reboot...
One of the suggested solutions to this problem is to turn off PCIe 4.0 via the BIOS.
I have an X570 Aorus Elite Motherboard which supports PCIe 4.0. To turn it off, do I choose "Gen 3"? Mine is current set to "Auto".
The advice isn’t applicable to your hardware. While your motherboard might support PCIe 4.0 your processor doesn’t support it. Which means it doesn’t matter what option you select, because PCIe 4.0, is already disabled.
My guess to why I'm missing Gen 3 is because I'm using a AMD Ryzen 2700x. It could be that Ryzen 2*** series CPU's don't support Gen 4?
You indicated you can select PCIe 3.0, your unable to select any revision of PCIe, that your hardware doesn’t actually support. Your processor doesn’t actually support PCIe 4.0
You can try and explicitly select PCIe 3.0 but it doubt it will make a difference. You indicated the GPU works some of the times, if this problem was caused by a firmware setting, you likely would have been required to explicitly configure the slot to get it working initially.
If anyone has other suggestions for 5700XT fixes, please let me know. This is driving me crazy.
It sounds like this problem is something that has recently started to happen which indicates it’s a driver issue not a hardware issue. One way to verify that’s the case is to reinstall Windows, install the same AMD display drivers, and see if the problem can be reproduced.
If you can reproduce the issue, that’s an indication you have a hardware problem, likely caused by the GPU starting to fail. It can indeed be possible for a GPU to work, unless you are explicitly exercising the problem silicon, which would not happen, without running software that requires that silicon. If this problem happens without running software that changes the troubleshooting steps considerably.
Best Answer
There are two ways a motherboard can provide more PCI-e lanes then the chipset provides:
Y
shape. The bottom of the Y can be 16 PCI-e lanes connected to the normal places on the motherboard (e.g. to the chipset or to the CPU). The upper two parts of the Y also provide 16 lanes but can not sustain full thoughput from both cards to the rest of the system of both at the same time. However it will work fine when sum of the bandwitdh of the 'upper Y connection' does not permanently exceed the based bandwitdh.This can work fine if both cards want fast but bursty data.
Edit: some of those switches also allow card-to-card PCI-e connections. This is relevant because a common setup is to have two GPU's connected via PCI-e. (NVidia SLI, AMD XDMA). In such cases, bandwidth to the rest of the desktop is less of a constraint.