[SOLVED] Motherboard PCI-E x16 speed for GPU

[Finnithnel]

Hello,

I have a Gigabyte Z390 Designare motherboard with the following setup :
- CPU : Intel Core i7-9700K Desktop Processor 8 Cores up to 4.9 GHz Turbo unlocked LGA1151 300 Series 95W

• 1st PCIE slot : MSI RTX 2080 Super Sea Hawk EK X
• 2cnd PCIE slot : empty
• 3rd PCIE slot : empty

• M2M : ADATA XPG SX8200 Pro 1TB 3D NAND NVMe Gen3x4 PCIe M.2 2280 Solid State Drive R/W 3500/3000MB/s SSD (ASX8200PNP-1TT-C)
• M2P : ADATA XPG SX8200 Pro 1TB 3D NAND NVMe Gen3x4 PCIe M.2 2280 Solid State Drive R/W 3500/3000MB/s SSD (ASX8200PNP-1TT-C)

• SATA 0 : empty
• SATA 1 : Samsung SSD 860 EVO 4TB 2.5 Inch SATA III Internal SSD (MZ-76E4T0B/EU)
• SATA 2 : Samsung SSD 860 EVO 4TB 2.5 Inch SATA III Internal SSD (MZ-76E4T0B/EU)
• SATA 3 : Samsung SSD 860 EVO 4TB 2.5 Inch SATA III Internal SSD (MZ-76E4T0B/EU)
• SATA 4 : empty
• SATA 5 : empty

Sata drives are setup as per my understanding of the mobo manual (page 29)
If I'm not wrong, M2M PCIE drive share bandwidth with SATA 4 & 5 while M2P PCIE share with SATA 0
It should mean that in my current configuration, there should be no share issue

When I set the PCIE x4 Switch to PCH Side, I get the following information in the BIOS :
PCIEX16 : PCIe 3.0 x16 @ 1.0 x16
PCIEX8 : N/A
PCIEX4 : N/A
PCIEX1_1 : N/A
PCIEX1_2 : N/A

M2M : ADATA SX8200PNP NVMe 3.0 x4 @ 3.0 x4
M2P : ADATA SX8200PNP NVMe 3.0 x4 @ 3.0 x4


When I set the PCIE x4 Switch to CPU Side, it becomes :
PCIEX16 : PCIe 3.0 x16 @ 1.0 x8
PCIEX8 : N/A
PCIEX4 : N/A
PCIEX1_1 : N/A
PCIEX1_2 : N/A

M2M : ADATA SX8200PNP NVMe 3.0 x4 @ 3.0 x4
M2P : ADATA SX8200PNP NVMe 3.0 x4 @ 3.0 x4

What I don't get is why I can't get my GPU, which should be a GEN3, to run at 3.0 x16
Is there something I screwed up ? Am I supposed to remove some devices to free some lanes ?

 

[SkyNetRising]

In low power mode GPU may switch to lower PCIE version mode.
It will switch to PCIE 3.0, when it's necessary for the workload.

 

[Finnithnel]

How can i verify that it indeed switch to PCIE 3.0 when needed ?

 

[SkyNetRising]

Open GPU-Z, look for bus interface info.
Then launch some graphically demanding game and watch, how bus interface info changes in GPU-Z.