PCIe Gen5 SSDs and PCIe Gen4 graphic cards... how not too loose half of the lanes?

Computers & Hardware
1

Dear all,

please, could you share some experiences about the new and much faster SSDs using the PCIe Gen5? This new Generation of PCIe interfaces allows much faster reading and writing of data (e.g. a Crucial T700 with 11.700 MB/s reading and 9.500 MB/s writing). There’s a special slot for such SSDs on new mainboards that support PCIe Gen5. However, when putting a graphic card, such as the RTX 4090, into the the PCI Gen5 slot for graphic cards, it’s said that this reduces the speed by 50% as only half of the lanes could be used by the SSD anymore (as it has to share all lanes with the graphic card). Hence, would it be a solution to put the graphic card into a PCIe Gen4 slot that is not directly linked to the CPU (as it’s the case for the PCIe Gen5 slots for graphic card and SSD)? Such PCIe Gen4 slots are using the mainboard’s processor, for example, Intel’s Z790, instead. Would this too much slow down the data transfer to and from the graphic card? Please, what’s your opinion?
Thank you all for your feedback in advance!
Best,
Wolfgang

2

@WolfgangSchafer When testing the performance of Depthkit captures, we monitor CPU usage, GPU usage, and disk usage. In nearly all tests which use an SSD connected to a high-speed interface (M.2 or SATA), the system’s capture performance is never constrained by the disk’s write speeds, but rather CPU and GPU bandwidth. My best guess is that using only the GPU in the PCI Gen5 slot, and writing to an SSD connected to a different interface will give you the best performance, but I encourage you to test different arrangements of the PCIe hardware to know for sure.

To help others weigh in, please provide the following:

  • Motherboard model
  • CPU model
  • GPU model
  • SSD model
  • Any other PCIe devices installed in the computer (such as the StarTech USB PCIe Card approved for use with Depthkit)
  • How many sensors are you capturing?
  • Where are you seeing these performance constraints?