Looking for PCIe 16x to 8x Adapter recommendations


Joseph

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Hi unRAIDers,

 

My main unRAID box has onboard video for basic viewing only and several 8x PCIe slots. I want to add a beefy GFX card (perhaps a Geforce 1080ti) to help with video transcoding/streaming. Can anyone share their experiences with 16x to 8x adapter cards and/or offer a recommendation for adding a GFX card? Many Thanks!

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3 minutes ago, jbartlett said:

PCIe slots are downward compatible. If the video card can plug into the slot, it should work though to a lesser capacity.

Thanks for your prompt reply. I didn't realize you could just plug a 16x into an 8x slot. I thought the teeth on the 16x would hit the back side of the 8x slot preventing it from properly seating in the slot.

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Word of warning, the GTX/RTX lines are limited to 2 streams at a time, and you would have to run it in a windows VM to get that.  If you want more, you have to look at a P2000 or similar professional grade GPU.  Just making sure you know the limitations before you go too far down the path, if you are fine with 2 streams and a windows VM then great!

 

I don't think a 16x card can slot into an 8x slot, unless it is a special slot that has the back "opened".  PCI-E will use the available lanes if you can seat it, so there is no electrical issue with running a 16x card in that slot...but you have to get the physical ability to plug it in!

Edited by Tybio
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1 hour ago, Tybio said:

Word of warning, the GTX/RTX lines are limited to 2 streams at a time...

Good to know, thank you. Sounds like I need to do more research before I get one.

 

1 hour ago, Tybio said:

I don't think a 16x card can slot into an 8x slot, unless it is a special slot that has the back "opened". 

That's what I thought, which is why I was looking for a 16x to 8x adapter.

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39 minutes ago, mrbilky said:

If your willing there are many videos on the topic most show how to remove the back of the 4x or 8x slots so you can insert the larger device

I've seen the videos... thanks, but not gonna risk damage to my server mobo by cutting off the back end of a slot bracket or a 16x PCIe card by sawing off the "extra" teeth🔨 😲; which is why I was looking for a 16x to 8x adapter. 😆

Edited by Joseph
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Amazon has quite a few options:  https://www.amazon.com/Express-Riser-Extender-Ribbon-Cable/dp/B06Y14G61W

 

I don't think you will find a riser card as the bracket on the back wouldn't work properly, and 16x cards can't support themselves in a vertical install without the bracket screw or the "tail" of the bracket seating solidly against the case.  I think your getting into custom work here, and a ribbon would make more sense as you can then mount the card elsewhere....sort of like the vertical mounts for the define R6.

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6 minutes ago, Joseph said:

I've seen the videos... thanks, but not gonna risk damage to my server mobo by cutting off the back end of a slot bracket or a 16x PCIe card by sawing off the "extra" teeth🔨 😲; which is why I was looking for a 16x to 8x adapter. 😆

HaHa yeah I hear ya on that but some like to live on the edge😎

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1 minute ago, Tybio said:

Amazon has quite a few options... and a ribbon would make more sense as you can then mount the card elsewhere....sort of like the vertical mounts for the define R6.

I'm with you on the ribbon cable idea, it does makes more sense so a card can be mounted elsewhere in the chassis. The ones I saw on amazon had mixed reviews, and my nephew says he's never been able to successfully get one to work; which is why I created this thread. I might be looking at just waiting it out until I get an upgraded server that properly supports 16x cards. 😕

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Some of the ribbon cables have external power the gets injected, not sure it that will help. No experience with them though.

I went the cut the back of the slot route. If you are good with a Dremel then it's pretty easy actually. If you decide to go down that route I can give some tips. The main point is the direction of the cut. It's easier to explain with a picture.

Also if you use a Linux VM there is a patch that allows more than 2 streams.
 

Found the cutting tip (click me). If you do it this way and don't let the dremel slip or better yet protect the surrounding area with a couple layer of tape. It's almost foolproof as you're just slowly taking away the plastic until you get to the slot. This is at your own risk of course. But as the saying goes no risk, no reward. As long as you've used a dremel before it shouldn't be a problem. If you have never used a dremel then maybe practice on something else first.

Edited by bnevets27
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9 hours ago, bnevets27 said:

Also if you use a Linux VM there is a patch that allows more than 2 streams.

That's true, but I believe that you can only /encode/ under linux in Plex at the moment...it's all sorts of early days on this, and not getting better quickly.  The only reliable non-hackish ways to do more than 2 streams is with an iGPU or a P2000.  It can work in other situations, but the fragility and potential for down-stream breakage is a factor.

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26 minutes ago, Tybio said:

That's true, but I believe that you can only /encode/ under linux in Plex at the moment...it's all sorts of early days on this, and not getting better quickly.  The only reliable non-hackish ways to do more than 2 streams is with an iGPU or a P2000.  It can work in other situations, but the fragility and potential for down-stream breakage is a factor.

100% agree, but the cost is frequently free. A lot of people have nvidia cards that are capable (hardware wise) of a bunch of streams (with the limit removed) laying around. Or can be had for dirt cheap. So even if it crashes and burns later on, there is little to no loss. And it is true that currently you can only encode on linux, but transcoding is a bit heavier on the encoding side rather then decoding (ignoring HEVC). And decoding should be getting added at some point. From what I've read it's techinally possible they just having built ffmpeg with the flag "decode=true"

Personally I don't want to run plex in a windows VM, too resource heavy for just running plex and windows being windows. Not saying its bad just not how I want to run plex. I'm waiting for drivers in unraid to allow hardware passthrough into dockers. That personally the only way I want to run it.

But the best supported way is exactly as you said P2000 or iGPU in a Windows VM.

Also since the OP didn't mention Plex. I think emby/jellyfin supports both encode and decode on linux.

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3 minutes ago, bnevets27 said:

And it is true that currently you can only encode on linux, but transcoding is a bit heavier on the encoding side rather then decoding (ignoring HEVC). And decoding should be getting added at some point. From what I've read it's techinally possible they just having built ffmpeg with the flag "decode=true"

Also since the OP didn't mention Plex. I think emby/jellyfin supports both encode and decode on linux.

So nvidia cards can't be used with these unRAID dockers: EMBY (to transcode) or Handbrake (to encode x265)?

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