Question GPU running at wrong PCI speed

[xtremexyz]

Hi,

My GPU is running at PCIe x8 3.0 according to GPU-Z when it should be running at x16. I don't know what the reason for this is, my GPU is installed at the very first PCIe x16 slot. I have a WiFi card installed at the second PCIe x16 slot and a USB 3.0 expansion card at the x1 slot. Could that be the reason why the GPU isn't running at x16?

I went to BIOS and set the PCI_E1 gen to gen 3 yet that didn't change anything, it is currently set to Auto. Everything else in the PCI tab is set to Auto.

I had reseated the GPU and the other cards in their slots beforehand so I don't know what to do here.

Help will be appreciated. Thanks.

Specs:

Motherboard: MSI B450 Tomahawk
CPU: Ryzen 5 3600 3.6GHz
RAM: Corsair 2x16GB 3200MHz Vengeance LPX DDR4
GPU: Asus Dual RX 6650XT OC
OS: Windows 11 Pro

 

[Lutfij]

According to your motherboard manual, which slots are you populating on the motherboard? What BIOS version are you currently on for your motherboard?

 

[rgd1101]

AMD Radeon RX 6650 XT Specs

AMD Navi 23, 2635 MHz, 2048 Cores, 128 TMUs, 64 ROPs, 8192 MB GDDR6, 2190 MHz, 128 bit

www.techpowerup.com

Bus Interface
PCIe 4.0 x8

 

[Barty1884]

My GPU is running at PCIe x8 3.0 according to GPU-Z when it should be running at x16.

No, it shouldn't.

AMD Radeon RX 6650 XT Specs

AMD Navi 23, 2635 MHz, 2048 Cores, 128 TMUs, 64 ROPs, 8192 MB GDDR6, 2190 MHz, 128 bit

www.techpowerup.com

Bus Interface
PCIe 4.0 x8

See this. Physically, that card only has a x8 pinout. PCIe 4.0 x8 = PCIe 3.0 x16 in terms of bandwidth, but if you've only physically got x8, dropping form 4.0 to 3.0, 3.0 x8 is all you can do.

 

[thestryker]

Hi,

My GPU is running at PCIe x8 3.0 according to GPU-Z when it should be running at x16. I don't know what the reason for this is, my GPU is installed at the very first PCIe x16 slot. I have a WiFi card installed at the second PCIe x16 slot and a USB 3.0 expansion card at the x1 slot. Could that be the reason why the GPU isn't running at x16?

I went to BIOS and set the PCI_E1 gen to gen 3 yet that didn't change anything, it is currently set to Auto. Everything else in the PCI tab is set to Auto.

I had reseated the GPU and the other cards in their slots beforehand so I don't know what to do here.

Help will be appreciated. Thanks.

Specs:

Motherboard: MSI B450 Tomahawk
CPU: Ryzen 5 3600 3.6GHz
RAM: Corsair 2x16GB 3200MHz Vengeance LPX DDR4
GPU: Asus Dual RX 6650XT OC
OS: Windows 11 Pro

While others have already answered regarding the video card being x8 I would like to mention that the only PCIe slot on your motherboard coming from the CPU is the first one so populating any of the other slots wouldn't make a difference.

 

[Deleted member 2947362]

My GPU is running at PCIe x8 3.0 according to GPU-Z when it should be running at x16.

GPU-Z is just showing you the max supported speed of the PCIe controller

The card has been hard wired to x8 PCIe 4.0 so if the card is populated in an x16 PCIe 4.0 slot that will be equal to x16 3.0 bandwidth.

X8 in PCIe 3.0 you probs don't lose much at 1080p ultra but it prob's effects performance when going much higher in resolution

but I am just speculating.

 

[Deleted member 2947362]

I went to BIOS and set the PCI_E1 gen to gen 3 yet that didn't change anything, it is currently set to Auto. Everything else in the PCI tab is set to Auto.

Also leave all those settings on Auto this will make sure SAM works

Manually setting those can disable SAM support on un-supported Chipsets with some motherboards
SAM can also be enabled on B350 Chipsets in the Bios and AMD software in Windows 10 (requires a reboot) and Windows 11 (doesn't require a reboot)

Make sure you have Resize bar and Above 4G enabled in the Bios

And in the AMD driver control panel under performance, tune, make sure SAM is enabled.

I can only assume they can get SAM working on B350/B450/X370 motherboards If the CPU has an PCIe 4.0 controller that's running an PCIe 4.0 graphic's card in an PCIe 3.0 Slot they can still connect the CPU to the GPU's DDR6 RAM via some trickery on the PCIe 4.0 Bus the card and CPU are connected?

But please correct me if I'm wrong as this is my own take from messing around with SAM and how they get it to work on an B350 chipset motherboard with PCIe 4.0 CPU and GPU like with my PC config for example.