AMD 9xxx and X870 pcie lanes

[MxPhenom 216]

Okay, do I understand this correct?

If you have a gen5 GPU, obviously that's 16 lanes. Sweet

Now most motherboards have 4 m.2. with first one supporting gen5 x4 from CPU. Then there's 2 m.2 that also support gen5 x4 from CPU but using those will take away lanes from GPU. Then another m.2 tied to the SB chipset.

Now with the 2 other m.2 wired to CPU, If you occupy one of those with a gen4 drive, does that still take lanes away from GPU? Seems pretty limited unnecessarily if I understand all this right.



Edit:
Above is referencing Gigabytes boards
Seems like Asus does this better. Where it has 2 m.2 at gen4 coming from chipset (gigabyte only has 1), so for someone like me where I plan to run a gen5 nvme and 2 (slots 3 and 4) gen4 and don't want to pull any lanes from the GPU. Then this board will do it as long as I don't populate the 2nd m.2 that's also wired to CPU.

 

[Knight47]

X870(without E) is basically a B650/B850.

Cpu has 5.0 x16 for gpu and two 5.0 x4(NVMe or USB4). Chipset has two 4.0 x4 and one 3.0x4(or 4 Sata)

Which board are you looking at?

 

[MxPhenom 216]

X870(without E) is basically a B650/B850.

Cpu has 5.0 x16 for gpu and two 5.0 x4(NVMe or USB4). Chipset has two 4.0 x4 and one 3.0x4(or 4 Sata)

Which board are you looking at?

Gigabyte x870e pro or x870 elite, and then x870 Strix A

Gigabytes sounds like if I only use M2_1 with a gen5 it shouldnt pull lanes from GPU. But if you were to use both M2_1 and M2_2 and/or M2_3 then it will.

 

[Deleted member 245263]

those overpriced atx boards feature build in bifurcation adapter, because there are suckers still buying atx in 2025?

 

[thesmokingman]

Gigabytes sounds like if I only use M2_1 with a gen5 it shouldnt pull lanes from GPU. But if you were to use both M2_1 and M2_2 and/or M2_3 then it will.

Can the gpu even saturate the lanes?

 

[Knight47]

Gigabyte x870e pro or x870 elite, and then x870 Strix A

x870 elite is just wasting lanes and has only 2 m.2 without sharing gpu lanes.
x870e pros is even worse, like what are they doing? 3.0 x1 is enough for lan and wifi, but they use 4.0 lanes instead. Again only two m.2 slots without stealing gpu lanes, you need to use those passive PCIe x4 to m.2 adapters for one 4.0 and one 3.0 NVMe(so one 5.0, two 4.0 and one 3.0 m.2 with adapters).

x870 Strix A has one m.2 from cpu and two from chipset.

I would rather buy a Asus TUF B850-Plus (two m.2 cpu, one from chipset) or TUF/Prime Pro X670E if you want 4-6 m.2 without cutting gpu lanes

 

[MxPhenom 216]

x870 elite is just wasting lanes and has only 2 m.2 without sharing gpu lanes.
x870e pros is even worse, like what are they doing? 3.0 x1 is enough for lan and wifi, but they use 4.0 lanes instead. Again only two m.2 slots without stealing gpu lanes, you need to use those passive PCIe x4 to m.2 adapters for one 4.0 and one 3.0 NVMe.

x870 Strix A has one m.2 from cpu and two from chipset.

I would rather buy a Asus TUF B850-Plus (two m.2 cpu, one from chipset) or TUF X670E if you want 4-6 m.2 without cutting gpu lanes

Yeah that's what I'm saying. Idk what Gigabyte are doing on these boards.

I'm going for a white board if you haven't noticed. So Strix is it unless I go to MSI or Asrock

 

[Knight47]

Yeah that's what I'm saying. Idk what Gigabyte are doing on these boards.

I'm going for a white board if you haven't noticed. So Strix is it unless I go to MSI or Asrock

ASRock B850 Steel Legend WiFi looks like the best pick, if you don't mind if it kills your cpu.

 

[Zach_01]

On Asrock X870E NOVA you can populate all 5 m.2 slots without loosing anything including sharing the x16 on the GPU slot.