Am i running out of PCI-E lanes?

schmolch · 01-13-2024, 08:04 PM

Hello everybody,

after adding a 3rd GPU (for a total of 7 4k displays) i had all my usb2 ports dying IF i also used my pci-e wlan/bluetooth card.
The error i get during bootup is

Code:

xhci_hcd 0000:16:00.0: Max number of devices this xHCI host supports is 127

even though i only use 3 usb devices (mouse, keyboard, pen-display).
It turned out the usb2-ports are now working again after i disabled onboard ethernet and onboard audio in the bios, but i dont really know for sure if thats the reason.

Someone suggested i might be running out of pci-e lanes and i looked at lspci, but there are many things i dont understand such as "does audio on my gpus count?" or "is every entry 1 lane regardless of Width"?

Anyway, this is my hardware:

Ryzen 5700g (APU) on MSI B550 gaming plus with 64GB ram
NVME-SSD (which is directly connected to the cpu AFAIK)
Radeon rx6600
Radeon rx460
PCI-E WLan/Bluetooth Card (intel)

This is the output of "lspci -vv | grep -P "[0-9a-f]{2}:[0-9a-f]{2}\.[0-9a-f]|LnkSta:"

Code:

00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne Root Complex
00:00.2 IOMMU: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne IOMMU
00:01.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge
00:01.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Renoir PCIe GPP Bridge (prog-if 00 [Normal decode])
		LnkSta:	Speed 8GT/s, Width x8
00:02.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge
00:02.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne PCIe GPP Bridge (prog-if 00 [Normal decode])
		LnkSta:	Speed 8GT/s, Width x4
00:02.2 PCI bridge: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne PCIe GPP Bridge (prog-if 00 [Normal decode])
		LnkSta:	Speed 8GT/s, Width x4
00:08.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge
00:08.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Renoir Internal PCIe GPP Bridge to Bus (prog-if 00 [Normal decode])
		LnkSta:	Speed 8GT/s, Width x16
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller (rev 51)
00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge (rev 51)
00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 0
00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 1
00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 2
00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 3
00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 4
00:18.5 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 5
00:18.6 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 6
00:18.7 Host bridge: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 7
10:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 XL Upstream Port of PCI Express Switch (rev c7) (prog-if 00 [Normal decode])
		LnkSta:	Speed 8GT/s (downgraded), Width x8
11:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 XL Downstream Port of PCI Express Switch (prog-if 00 [Normal decode])
		LnkSta:	Speed 16GT/s, Width x16
12:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Navi 23 [Radeon RX 6600/6600 XT/6600M] (rev c7) (prog-if 00 [VGA controller])
		LnkSta:	Speed 16GT/s, Width x16
12:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Navi 21/23 HDMI/DP Audio Controller
		LnkSta:	Speed 16GT/s, Width x16
16:00.0 USB controller: Advanced Micro Devices, Inc. [AMD] 500 Series Chipset USB 3.1 XHCI Controller (prog-if 30 [XHCI])
		LnkSta:	Speed 8GT/s, Width x4
16:00.1 SATA controller: Advanced Micro Devices, Inc. [AMD] 500 Series Chipset SATA Controller (prog-if 01 [AHCI 1.0])
		LnkSta:	Speed 8GT/s, Width x4
16:00.2 PCI bridge: Advanced Micro Devices, Inc. [AMD] 500 Series Chipset Switch Upstream Port (prog-if 00 [Normal decode])
		LnkSta:	Speed 8GT/s, Width x4
20:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43ea (prog-if 00 [Normal decode])
		LnkSta:	Speed 2.5GT/s, Width x4
20:07.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43ea (prog-if 00 [Normal decode])
		LnkSta:	Speed 5GT/s, Width x1
21:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Baffin [Radeon RX 460/560D / Pro 450/455/460/555/555X/560/560X] (rev cf) (prog-if 00 [VGA controller])
		LnkSta:	Speed 2.5GT/s (downgraded), Width x4 (downgraded)
21:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Baffin HDMI/DP Audio [Radeon RX 550 640SP / RX 560/560X]
		LnkSta:	Speed 2.5GT/s (downgraded), Width x4 (downgraded)
22:00.0 Network controller: Intel Corporation Wi-Fi 6 AX210/AX211/AX411 160MHz (rev 1a)
		LnkSta:	Speed 5GT/s, Width x1
23:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981/PM983 (prog-if 02 [NVM Express])
		LnkSta:	Speed 8GT/s, Width x4
30:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cezanne [Radeon Vega Series / Radeon Vega Mobile Series] (rev c8) (prog-if 00 [VGA controller])
		LnkSta:	Speed 8GT/s, Width x16
30:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Renoir Radeon High Definition Audio Controller
		LnkSta:	Speed 8GT/s, Width x16
30:00.2 Encryption controller: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 10h-1fh) Platform Security Processor
		LnkSta:	Speed 8GT/s, Width x16
30:00.3 USB controller: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne USB 3.1 (prog-if 30 [XHCI])
		LnkSta:	Speed 8GT/s, Width x16
30:00.4 USB controller: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne USB 3.1 (prog-if 30 [XHCI])
		LnkSta:	Speed 8GT/s, Width x16

There are 22 "LnkSta:" lines, does this mean i use 22 out of 24 PCI-E Lanes?

Thank you very much for any reduction of my stupidity.

GlennsPref · 01-13-2024, 08:32 PM

Hi,this may not be your answer,but I recently installed a corsair nvme 2Tb ssd and a

similar thing happened to my wifi/bt pcie card.

I had plugged the nvme drive into a spare slot, one under a heatsink, and the one I was attempting to install to out in the open.

I removed the corsair nvme drive and wifi worked again.

I then installed it under the heatsink and the wifi/bt card came back to life.

I hope this helps.

obobskivich · 01-20-2024, 01:18 AM

Looks like the videocards are negotiating to 8+4 in expansion slots, and onboard devices are taking up the rest. I've never seen this kind of instability from having two or three (working and similar) GPUs in a system, but I have seen it from having composite USB devices and/or composite PCIe devices (e.g. those 'do 50 things in one' card that offer SATA, WiFi, BT, 56k modem, coffee maker, etc on one card, or as one USB plug-in), which usually assume a proprietary Windows driver to make the whole mess work. I would start removing things step-by-step and figure out when it all starts working again, and then figure out which device is consistently the conflict - hopefully its something simple like the WiFi card (since those aren't horribly expensive).

Out of curiosity: It's been a while since I've played around with this, but I know some of the higher end Radeon cards can do 6 monitors all on their own (I have a 'semi-pro' Vega Frontier Edition, and it can do this) via MST with a hub - I never had good luck finding a quality hub, but it may be worth looking into if either of your Radeon cards can do that, because you could potentially drop the other one (I'm assuming you're using one or more monitors from the APU as well, since you mentioned 'third' graphics card).

Also note on the newer Radeons, they're kind of confusing in how they'll appear in lspci - they have a PCIe switch internally, so they interface at x16 to the system, but then split that up inside for whatever functions. So look at the 'upstream' and 'downstream' there - it looks like that card is being hooked to the system at x8, which with the other card (which is reporting x4) you've got 12 lanes used, the NVMe looks like its grabbing another 4, and everything else is probably onboard devices + the WiFi.