A Patch Is Still Pending For Fixing Up Newer Radeon GPUs In Older Motherboards

[phoronix]

Phoronix: A Patch Is Still Pending For Fixing Up Newer Radeon GPUs In Older Motherboards

Besides the mysterious EXT4 issue on Linux 4.19 that is still being sorted out, another known issue but with a fix pending that is hopefully not far out pertains to running newer Radeon graphics cards with older motherboards...

http://www.phoronix.com/scan.php?page=news_item&px=Linux-PCIe-Link-Snafu

[Beherit]

Perhaps this will fix problems with my RX 580 card using any kernel newer than 4.18.

Glad this will be backported! Then again, I nearly completely skipped 4.19 already so perhaps I'll just wait for 4.20 to go RTM.

[puleglot]

The number of users with PCI Express 3.0 graphics cards and still using PCI Express 1.0 motherboards is to some surprise still up there given the reports of GPU fatal errors on Linux 4.19 and early 4.20 release candidates, PowerPlay regressions, etc.

Motherboards with PCI-E 2.0 are also affected by this bug.

[ms178]

Is this bug Linux specific? It could also explain some weird behaviour which I've noticed with mGPU setup of 2 x RX 570s during the last week on Windows on my X58 system. I would expect it to work in x8, x8 mode but with the respective setting in the BIOS on Auto it was set to x16, x8 by default and got some very strange behaviour in Battlefield 1 which looked like syncing issues between the cards, not just major stuttering but also pauses and freezes and also some defective graphical errors with heavy blinking which I suppose would come from a defective card. This was on a Samsung S24F356FHU (HDMI) with FreeSync enabled. Everything is fine though while using these cards as a single device seperatly. But even if I force x8, x8 mode in BIOS I couldn't get it to work reliably in BF1.

[ms178]

You can assume that Linux users do not know. The amdgpdu driver does not support crossfire. We sell old hardware and buy faster and better hardware and do not try tricks that do not work even in other operating system.

Okay, probably it is better suited for another forum. I just wanted to mention it that both cards had a manufacturing date from June 2018 and had probably the newer chip revision. As PCIE 3.0 cards should be perfectly downwards compatible with PCIE 2.0 slots, I'd just assume that there should be no problems with older and still fast enough hardware.

[PuckPoltergeist]

Is this bug Linux specific?

Pretty sure, it's a bug in the Linux PCIe driver.

[Beherit]

Is this bug Linux specific?

Yeah, it's a software driver issue. I never had any problems prior to kernel 4.19.