Advice on PCI-e Lanes in Ryzen 7

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1

Hey guys, I need some advice in counting pci-e lanes… I’m (slowly) putting a system together and I pretend to buy a Ryzen 7 + Vega64 so it can last me for many years.

My question is, in the specs, Ryzen has only 20 pci lanes 3.0, besides the GPU to be added I already have a M.2 NVMe and a Wifi+BT card and ideally I would love to add another M.2 1T SATA for my projects avoiding have 2,5" drives in my system… would I have enough PCI lanes for that?

Here is my problem, the motherboard B450 I’m looking to buy (this one) has enough slots for the 2 M.2, WIFI and GPU --as far I understood-- in this config:

  • M.2_1 PCI 3.0 x4 (NVMe)
  • M.2_2 PCI 2.0 x4 (SATA and though chipset)
  • GPU PCI 3.0 x16
  • WIFI+BT PCI 2.0 x1

In my understand Ryzen would NOT have enough lanes for all of this at maximum speeds, so my GPU would be running at x8 3.0 in this case?

Would this bottleneck the Vega performance (for games, video edit/rendering)??
And does the M.2_2 passing through the chipset impact at all the other ones, or should I not count it using the 20 lanes from Ryzen?

I’m lost in my counts… last time I built a computer myself was early 2000s and things were much much simpler back then. I’m still trying to catch up with all the new tech (for me).

EDIT: Or should I go Threadripper?

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Depending on your MoBo.

You can run your GPU x8 and have the M.2 run directly to the CPU but in that case you have to check out what MoBo you use and which Lanes run in the CPU and which run to the Chipset.

So next Step:

Choose a MoBo that fits.

3

Thanks @BookrV,

so, Am I interpreting right the MoBo I’ve linked previously (This one: https://www.msi.com/Motherboard/B450M-MORTAR-TITANIUM/Specification) or what you say is that it won’t fit for all those devices I’m trying to connect? Should I look to another one then?

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Going to check later.

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There will be diagram with the pcie lanes and chipset.

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Get a mobo with integrated Wi-Fi and BT.

One of your M.2 will be directly linked to the CPU on x4 3.0 speed, while the other will be through the chipset on x4 2.0 speeds.

Graphics card will still be x16 in this case, and even if it was x8 it wouldn’t be a bottleneck.

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Just like @anon46267848 said:

AMD® B450 Chipset
4 x SATA 6Gb/s ports1
1 x M.2 slot (M2_2, Key M)1
Supports PCIe 2.0 x4 2242/ 2260 /2280 storage devices
AMD® CPU
1 x M.2 slot (M2_1, Key M)*1
Supports PCIe 3.0 x4 and SATA 6Gb/s 2242/ 2260 /2280 storage devices
PCI_E4 slot will be unavailable when an M.2 SSD is installed in the M2_2 slot.

So 1 M.2 into the CPU 1 into the Chipset.

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If you want both M.2 going to the CPU and not through the chipset, there’s the C7H(WIFI).

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So what with what I see here, you should be able to utilize:

  • M2_1 Slot for your primary SSD
  • PCI_E1 at 3.0 the full x16
  • PCI_E3 for your WIFI+BT
  • M2_2 Slot which disables your PCI_E4 slot for the 2nd SSD

image
image.jpg1200x675 170 KB

Taken from toms hardware
Base on that image, you should have enough chipset lanes for everything you need.

1 Like
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Thanks a lot guys!! That clarify a lot of things for me!