PSA: PCIe risers (TLDR at end)

[Charlie22911]

For the last couple of days I’ve been troubleshooting very high DPC latency related to dxgkrnl.sys, Wdf001000.sys, and nvlddmkm.sys according to LatencyMon.
Some of the symptoms were horrible stuttering and crackling audio as well as visual corruption of video played through YouTube, 3D applications seemed to be unaffected.

This happened with two separate nVidia 1080tis as well as a nVidia 1060 6GB, but worked fine with a nVidia GT 710 and AMD 6970.
I tried reinstalling Windows 10, various driver versions, changing power profiles, disabling c states... nothing worked.

The positioning of the card in this build necessitated a PCIe x16 riser, so I ordered one of the Thermaltake risers and as a last resort I tried removing it (it either works or it doesn’t right?)... Well It worked perfect, so I reinstall the riser and manually set PCIe link speed to Gen 2 and again no issues! I suspect I received an old version of this riser that is not shielded since I ordered it from Amazon instead of Thermaltake directly.

I spent a pretty large amount of time digging through google results with no solution, so I’m posting this in the hopes it may help someone in the future who has similar issues.

TLDR: PCIe risers can cause problems that range from subtle to catastrophic. Such problems may be intermittent and hard to diagnose. Buy quality shielded stuff from a reputable brand.

 

[PingSpike]

Good info. I've often wondered about this kind of stuff since the level of quality of a lot of these risers looks pretty rough. Do you have a link to the actual riser you bought?

 

[Charlie22911]

Good info. I've often wondered about this kind of stuff since the level of quality of a lot of these risers looks pretty rough. Do you have a link to the actual riser you bought?

https://www.amazon.com/gp/aw/d/B06Y5YNGDJ/ref=yo_ii_img?ie=UTF8&psc=1

That is the exact one I ordered, I can’t discount the possibility that I got a bad riser since many people run them just fine.

 

[nathanddrews]

My guess is you just got a lemon. I think that's the same PCIe extension cable that Linus used in his video. He managed to get 4m of length before it stopped working correctly.

Spoiler: LTT YouTube

 

[eek2121]

My guess is you just got a lemon. I think that's the same PCIe extension cable that Linus used in his video. He managed to get 4m of length before it stopped working correctly.

Spoiler: LTT YouTube

He only tested a single 3D application, and furthermore, did not do any type of extensive testing. I would definitely NOT take the plunge until others have. I wish Anandtech would put some of these risers through the paces...it seems like Anandtech has so few resources that they are just lucky to cover the minimums these days...

 

[nathanddrews]

He only tested a single 3D application, and furthermore, did not do any type of extensive testing.

They only showed one test in that video, yes. LTT has built several of these wall-mounted computers with up to 1m PCIe riser/extensions and not reported any issues. In fact, within the first 45 seconds of the video I posted, they state that experienced "no performance degradation whatsoever and the system worked perfectly fine". I would expect that if LTT was seeing errors and glitches with any of their builds using these cables, they would report it. If it were an EMI problem, I would expect LTT HQ to have significantly more interference than a typical household would have.

I echo your wish for a thorough analysis by AT.

 

[4K_shmoorK]

I know there are alot of people that report issues with Gen 1/2 Thermaltake PCI extension cables. Gen 3 seems to be fine but they are charging $70 for it. Picking up a Thermaltake View 71 RGB and extension cable today from Microcenter.

 

[PingSpike]

Whew! $70 for an extension cable? Who do you think you are Thermaltake, Bestbuy?

 

[4K_shmoorK]

ｐｒｅｍｉｕｍ extension cable

 

[Charlie22911]

I ended up abandoning the ITX custom build path and instead put everything into a Silverstone FTZ01, which uses a hard right angled riser. It appears to be shielded via two ground planes in the PCB, so far I have not experienced any issues. I’ll try to do some things to load up the PCIe bus more with something like Shadowplay or video capture via the GeForce Experience overlay, but I don’t anticipate any issues.

 

[grant2]

This is a good PSA, thanks for the warning. If anyone comes across a testing or review resource for risers, that'd be awesome to get a link

 

[pseast]

For the last couple of days I’ve been troubleshooting very high DPC latency related to dxgkrnl.sys, Wdf001000.sys, and nvlddmkm.sys according to LatencyMon.
Some of the symptoms were horrible stuttering and crackling audio as well as visual corruption of video played through YouTube, 3D applications seemed to be unaffected.

This happened with two separate nVidia 1080tis as well as a nVidia 1060 6GB, but worked fine with a nVidia GT 710 and AMD 6970.
I tried reinstalling Windows 10, various driver versions, changing power profiles, disabling c states... nothing worked.

The positioning of the card in this build necessitated a PCIe x16 riser, so I ordered one of the Thermaltake risers and as a last resort I tried removing it (it either works or it doesn’t right?)... Well It worked perfect, so I reinstall the riser and manually set PCIe link speed to Gen 2 and again no issues! I suspect I received an old version of this riser that is not shielded since I ordered it from Amazon instead of Thermaltake directly.

I spent a pretty large amount of time digging through google results with no solution, so I’m posting this in the hopes it may help someone in the future who has similar issues.

TLDR: PCIe risers can cause problems that range from subtle to catastrophic. Such problems may be intermittent and hard to diagnose. Buy quality shielded stuff from a reputable brand.

These cables are apparently very good quality and are said to provide nearly 24GB/s lossless bandwidth per x16 card. http://www.amazon.com/dp/B07997W7PV