Question What motherboard do I need to get an x16 video card with an x8 capture card and an 1TB NVME

Sep 30, 2021
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Hey all!

New to this forum. I just purchased three used PC's to build 3 systems to put in capture cards for my virtual event company.

1. Ryzen 5800x, B550 mortar Wi-Fi motherboard, RTX3070, 1TB NVME, and I added a Blackmagic Decklink quad HDMI (x4) capture card.
2 & 3. Ryzen 3700x, B450 tomahawk max motherboard, RTX 2070 super, 1TB NVME, and I added a Blackmagic Decklink quad 2 (x8) capture card

The issue I'm having is that I believe I'm running out of PCIe lanes for all the devices. On the PC with the Ryzen 5800x the capture card works perfectly with 3 devices plugged in, if I try to plug in a fourth it slows down the video and the audio becomes jittery. On the two 3700x PC's I can plug in 6 devices to the capture cards, if I add more the same problem happens.

Reading a bit I see that theres PCI lanes for the CPU and PCI lanes for the chipset. I thought that between both I would have enough for everything to work correctly but apparently I'm wrong. Could you guys help me to understand what's wrong and hopefully make them work with what I have, or if its not possible point me on the right direction to what motherboard I need to get this to work correctly?

TIA for the help!
 
if you need speed on chipset lanes, then you might be out of luck, they are limited to x4 lane speed between chipset and CPU (no matter how many lanes chipset offers, bandwith is caped to x4)
so your solution would be CPU lanes
both ryzens you have gives your pcie devices just 16 lanes, so u might need to switch to HEDT (threadripper)
they go from 64 up to 128 pcie lanes from CPU
threadrippers use sockets sTR4 (TR1000/2000 serie) and sTRX4 (for TR3000 serie)

so working with what you have, you can use your GPU in x8 mode and that will free you up x8 lanes
 
Sep 30, 2021
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I believe they have 24 lanes each:

AMD Ryzen 9 3900X and Ryzen 7 3700X Review: Zen 2 and 7nm Unleashed - Tom's Hardware | Tom's Hardware (tomshardware.com)

would buying a mother board like this one:

Amazon.com: GIGABYTE X570 AORUS PRO Wi-Fi (AMD Ryzen 3000/X570/ATX/PCIe4.0/DDR4/USB3.1/Realtek ALC1220-VB/Fins-Array Heatsink/RGB Fusion 2.0/2xM.2 Thermal Guard/Gaming Motherboard) : Everything Else

that has a pci x16 slot AND a pci x8 slot with the 24 lanes for the CPU allow me have all my divices work?

if you need speed on chipset lanes, then you might be out of luck, they are limited to x4 lane speed between chipset and CPU (no matter how many lanes chipset offers, bandwith is caped to x4)
so your solution would be CPU lanes
both ryzens you have gives your pcie devices just 16 lanes, so u might need to switch to HEDT (threadripper)
they go from 64 up to 128 pcie lanes from CPU
threadrippers use sockets sTR4 (TR1000/2000 serie) and sTRX4 (for TR3000 serie)

so working with what you have, you can use your GPU in x8 mode and that will free you up x8 lanes
 

logainofhades

Titan
Moderator
4 of those lanes actually go to the chipset, from the CPU, leaving you with 20, for graphics and for your NVME storage. All other lanes are handled by the chipset itself.

 
ye, but for pci-e slots you have just x16 available...x4 for nvme and x4 for chipset
would buying a mother board like this one:

Amazon.com: GIGABYTE X570 AORUS PRO Wi-Fi (AMD Ryzen 3000/X570/ATX/PCIe4.0/DDR4/USB3.1/Realtek ALC1220-VB/Fins-Array Heatsink/RGB Fusion 2.0/2xM.2 Thermal Guard/Gaming Motherboard) : Everything Else

that has a pci x16 slot AND a pci x8 slot with the 24 lanes for the CPU allow me have all my divices work?
well even if it has:
Expansion Slots Integrated in the CPU (PCIEX16/PCIEX8):
  • 1 x PCI Express x16 slot, supporting PCIe 3.0 and running at x16 (PCIEX16)
  • 1 x PCI Express x16 slot, supporting PCIe 3.0 and running at x8 (PCIEX8)
  • For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.
  • The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When using the 3rd Generation AMD Ryzen™ processors/2nd Generation AMD Ryzen™ processors, the PCIEX16 slot operates at up to x8 mode.
thats still 16 lanes together...either one x16 or two x8

hmm even if x570 has more chipset lanes...they are still limited to x4 link from cpu
but b550 operates at pcie 3.0mode and x570 operates at 4.0 mode...which means x570 chipset has more bandwith on chipset lanes
so probably it could work...but im not sure if pcie 3.0 device will keep chipset link to cpu at 4.0 mode
maybe somebody has answer to that
 
Sep 30, 2021
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Is there any way to force the NVME to go through chipset lanes instead of CPU lanes so I have the 8 free lanes I need for the capture card?

ye, but for pci-e slots you have just x16 available...x4 for nvme and x4 for chipset

well even if it has:

thats still 16 lanes together...either one x16 or two x8

hmm even if x570 has more chipset lanes...they are still limited to x4 link from cpu
but b550 operates at pcie 3.0mode and x570 operates at 4.0 mode...which means x570 chipset has more bandwith on chipset lanes
so probably it could work...but im not sure if pcie 3.0 device will keep chipset link to cpu at 4.0 mode
maybe somebody has answer to that
 
nvme is 4 lanes..u can use adapter m2 to pcie...but its not 8 lanes
16lanes pcie slots (gpu mainly)
4lanes nvme
4lanes chipset

u cant force device to be either cpu or chipset...its physicaly wired either to cpu or to chipset
there are m2 slots connected to chipset, which will free you x4 lanes from cpu
 
Sep 30, 2021
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Ok, next question. If I set video card to x8 should it work?

x8 video card
x8 capture card
x4 chipset
x4 NVME

I've read that at x8 video card performance shouldn't be too hardly hit. Is this true?

Funny thing is, I set the x8 + x8 option on the bios and it still has the same issue.
 

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