This might be common knowledge for some, but I just wanted to share the results of an experiment I ran today. One of my main motivations to use unRAID is to run a bunch of VMs. Specifically, I want to run three OpenELEC VMs in addition to my other VMs. One of the challenges is the number of free PCIe slots for all the GPUs I need to passthrough. Eventually I'm going to buy an X99 motherboard with seven x16 slots, but for now I'm using an ASRock Z97 Extreme6 which has three x16 slots and two x1 slots. And remember that not all x16 physical slots have 16 lanes active.

 

On to my experiment....

 

I bought one of these:

http://www.amazon.com/Express-Powered-Extender-Litecoin-Bitcoin/dp/B00HH1MLGQ/ref=pd_sim_147_14?ie=UTF8&refRID=1SS42V0N98TVSFSB9HPM&dpSrc=sims&dpST=_AC_UL160_SR160%2C160_

 

I wanted to verify that my Radeon 6450 GPU would work just fine for OpenELEC when plugged into a PCIe x1 slot. The adapter is plugged into the PCIe 2.0 x16 (x2 electrically) slot on my motherboard which connects to the PCH. I believe this should represent the worst case scenario in terms of PCIe bandwidth since it's Gen 2 and going through the PCH.

 

The result was flawless playback of full bitrate bluray rips.

 

I also have one of these on order which is designed to allow a low-profile PCIe card to plug into a x1 slot and still be screwed down like a normal full height PCIe card.

http://www.newegg.com/Product/Product.aspx?Item=N82E16815158223

 

I think this is a good solution if you're out of x16 slots and want to add a GPU for less demanding applications like OpenELEC.

Hello MikeW

 

I haven't bought or tested one of these yet

 

My main purpose with getting one would be for putting multiple Hauppauge HVR-2250 cards into a VM

 

but if your Radeon 6450 GPU is working on a PCI-E1 slot ...

I'd be curious if they might work attached to something like this

 

http://www.aliexpress.com/item/Free-shipping-1-to-3-PCI-express-1X-slots-Riser-Card-PCIe-x1-to-external-3/32292624969.html

 

I can't remember the specific search terms I used, but several  months ago I found a few of these that were similar on AliExpress

 

not sure if it's a blind alley or useful one

 

Bobby

 

 

... My main purpose with getting one would be for putting multiple Hauppauge HVR-2250 cards into a VM

 

WHY would you buy these adapters then?    The HVR-2250 is a PCIe x1 card !!

 

[bTW, I have 4 2250's that I'm going to sell on e-bay in a couple weeks ... if you're interested PM me  (Just converted to an all cable-card setup) ]

 

 

As Gary said I don't see any advantage of using that expansion device unless you're out of PCIe slots. I was looking into something similar in order to expand the number of slots, but I don't know how well these would work with KVM and PCIe/GPU passthrough because there's probably a PCIe switch on the card. I have no idea if that prevents the additional slots from being split up and passed through to different VMs.

Hello

 

I am in the same boat. I am putting x16 video card in for OpenELEC VM and I would like to use second video card for Windows VM. However all I got left is one x1 PCI-E slot and one regular PCI slot.

 

Can anyone confirm that using x1 to x16 adapters is supported by Unraid VMs?

 

Is there any advantage of using the extender with the cable solutions over the riser card?

 

Do I need to look for anything specific in a x16 card I would purchase in order to work in x1 slot?

 

If I were to go the good old PCI route instead, does unraid VM support PCI video cards or do they have to be PCI-E?

 

thanks!

The question isn't whether UnRAID will work with the adapter => UnRAID will simply "see" whatever card is in the slot ... the question is whether the card will work okay.  It SHOULD ... as long as it meets the PCIe spec it should simply run with one lane instead of the 8 or 16 it's designed for.

 

A VM should work just fine with a PCI card as well.

 

Indeed. See my sig for the pci card I'm using. Low cost, low power, perfect for console and anything else not really needing heavy lifting.

Indeed. See my sig for the pci card I'm using. Low cost, low power, perfect for console and anything else not really needing heavy lifting.

 

thanks, I am looking for something with HDMI so I can send sound too. It will probably be hard to find PCI card with HDMI that's not expensive. Might just go the x1 to x16 adapter route.

Indeed. See my sig for the pci card I'm using. Low cost, low power, perfect for console and anything else not really needing heavy lifting.

 

thanks, I am looking for something with HDMI so I can send sound too. It will probably be hard to find PCI card with HDMI that's not expensive. Might just go the x1 to x16 adapter route.

You can also buy a x1 card  I use a Zotac gt720 card for openelec. I'll find the product number when I'm back home later this week.

 

The ZOTAC card comes in both x16 and x1 versions ... here's the x1 version:

 

http://www.amazon.com/ZOTAC-GeForce-Express-Graphics-ZT-71107-10L/dp/B00LZKWVJW

Traditionally the 1x cards have been so overpriced they made no sense to buy. Before the adapters became ubiquitous I saw some people had taken to sawing off the extra card length so that it would fit in a pci-e 1x slot or breaking the back of a 1x slot on a motherboard off so that the card could hang out the back. Believe it or not, both "solutions" were reported to work as expected.

Thanks for the replies. I did see x1 cards but they are way too expensive considering I only want super basic card for desktop use.

 

I saw some PCI cards with HDMI sold on ebay for $20-$30 so I set some alerts and hopefully I'll be able to snatch one in the future

 

Example:

http://www.ebay.com/itm/Graphics-Video-Card-PCI-GeForce-8400-GS-256mb-ddr3-HDMI-DVI-CRT-Desktop-/171911355463?hash=item2806b71c47&nma=true&si=ExPIdRv7lVqid2tyO%252BHe%252BSrWSQc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

VERY carefully cutting off the rear side of an x1 slot will allow an x16 card to be mounted in it, and this will work fine.    This is very easy with a Dremel tool ... but you do have to be very careful that you don't damage the electrical part of the slot.

 

You could also mod the PCIe slot by cutting a slot in the end of the PCIe socket so the card will fit.  The nice thing about PCIe is that any card will work in any slot just at a different speed.

 

Simalar to this.

 

https://www.google.com/search?q=PCIe+mod&client=ms-android-verizon&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMIyr_4mKfCyAIV1jSICh32UgU-&biw=360&bih=559#tbm=isch&q=PCIe+1x+mod&imgrc=l1G-UBCM10zvwM%3A

 

yeah I really don't want to do that. I just got new MOBO/CPU and with my luck I would shorten the whole thing out.

 

What sucks is that the MB actually has two x16 slots but I had to use one for x4 SATA controller. I also have to be careful with video cards that have oversized fans/heatsinks as all the slots will be used and they won't fit.

 

If I can't find cheap PCI card for a while I'll go the x16 with x1 adapter route. Are those made so that if I use low profile video card with the riser will it actually fit properly to a standard case?

If I can't find cheap PCI card for a while I'll go the x16 with x1 adapter route. Are those made so that if I use low profile video card with the riser will it actually fit properly to a standard case?

 

Some are (I know there is a kind of expensive startech one that bills itself doing this) most don't seem to take it into consideration.

 

Depending upon your case and card, an easy ghetto mod to use with this adapter is to use some stacked motherboard stand offs and possibly washers to artificially extend the backplate mounting screw hole to accommodate the additional height from the adapter. Then you can even use a full height card as long as your case has a little extra room above the cards.

 

Another thing to consider is supposedly 1x pci-e is only spec'ed for 30watt or something but the 16x graphics card slots are 70ish. A lot of the adapters now come with some kind of molex connector to maybe fix this but I have my doubts. I did run a 8800GT way back with an adapter and I sort of think that the extra graphics card power plug that was required by that card anyway was enough. I only ran 3dmark tests with it and besides the expected performance hit I didn't have trouble with my testing. Honestly, I suspect all the ports provide full power these days or something but I really have no idea. If you're using a low end card I just don't think this is going to matter either way.

 

This was kind of an uncommon idea back when I was playing around with it, but when bitcoin mining became huge there were a lot of people running boatloads of graphics cards in a single machine so this became pretty popular.

Regarding PCI cards:

The IOMMU specs essentially say that all PCI devices behind a bridge must be passed through together. So if you have 3 PCI slots they are almost certainly behind one bridge and therefore can only be passed together to one VM. So only buy 1!

 

I can't even get anything behind a PCI bridge to work with unraid/kvm passthrough on my board for some reason. It complains that the devices are in use/busy without the bridge included. But if I try to passthrough the associated bridge it tells me it doesn't exist (even though its listed in lspci). I even tried binding everything to pci-stub in the kernel options.

If I can't find cheap PCI card for a while I'll go the x16 with x1 adapter route. Are those made so that if I use low profile video card with the riser will it actually fit properly to a standard case?

 

Some are (I know there is a kind of expensive startech one that bills itself doing this) most don't seem to take it into consideration.

 

Depending upon your case and card, an easy ghetto mod to use with this adapter is to use some stacked motherboard stand offs and possibly washers to artificially extend the backplate mounting screw hole to accommodate the additional height from the adapter. Then you can even use a full height card as long as your case has a little extra room above the cards.

 

Another thing to consider is supposedly 1x pci-e is only spec'ed for 30watt or something but the 16x graphics card slots are 70ish. A lot of the adapters now come with some kind of molex connector to maybe fix this but I have my doubts. I did run a 8800GT way back with an adapter and I sort of think that the extra graphics card power plug that was required by that card anyway was enough. I only ran 3dmark tests with it and besides the expected performance hit I didn't have trouble with my testing. Honestly, I suspect all the ports provide full power these days or something but I really have no idea. If you're using a low end card I just don't think this is going to matter either way.

 

This was kind of an uncommon idea back when I was playing around with it, but when bitcoin mining became huge there were a lot of people running boatloads of graphics cards in a single machine so this became pretty popular.

 

Would it help if the video card had the 4-pin power connector in the back?

 

If I go the adapter route I will be looking for the cheapest most basic video card so hopefully the power need will be low.

Regarding PCI cards:

The IOMMU specs essentially say that all PCI devices behind a bridge must be passed through together. So if you have 3 PCI slots they are almost certainly behind one bridge and therefore can only be passed together to one VM. So only buy 1!

 

I can't even get anything behind a PCI bridge to work with unraid/kvm passthrough on my board for some reason. It complains that the devices are in use/busy without the bridge included. But if I try to passthrough the associated bridge it tells me it doesn't exist (even though its listed in lspci). I even tried binding everything to pci-stub in the kernel options.

 

hmm didn't know about this.

 

What I have is:

 

PCI-E 16

PCI-E 1

PCI-E 16

PCI

 

Should I be ok with one x16 video card and then either one x1->x16 video card OR PCI video card?

... Would it help if the video card had the 4-pin power connector in the back?

 

NO !!  You definitely don't want a card that requires auxiliary power.    The reason they have that power connection is that the card requires more power than the PCIe bus can provide.      Not really a factor here, however, as inexpensive cards like you're looking for aren't going to have this.

... Would it help if the video card had the 4-pin power connector in the back?

 

NO !!  You definitely don't want a card that requires auxiliary power.    The reason they have that power connection is that the card requires more power than the PCIe bus can provide.      Not really a factor here, however, as inexpensive cards like you're looking for aren't going to have this.

 

I agree the best overall bet is to get a low power card to use with the adapter. I think the 6450/5450 cards top out at like 20 watts load or something. I suspect nvidia has something similar.

 

That said, I ran that 8800GT card through a 16x -> 1x pci-e adapter and that had aux power and wasn't a low power card by any means. And it seemed to work fine. I couldn't say why though. I'd guess either the aux power made up for the shortfall or more likely in practice (at least some) motherboards actually provide the full 16x spec power to all the slots.

Regarding PCI cards:

The IOMMU specs essentially say that all PCI devices behind a bridge must be passed through together. So if you have 3 PCI slots they are almost certainly behind one bridge and therefore can only be passed together to one VM. So only buy 1!

 

I can't even get anything behind a PCI bridge to work with unraid/kvm passthrough on my board for some reason. It complains that the devices are in use/busy without the bridge included. But if I try to passthrough the associated bridge it tells me it doesn't exist (even though its listed in lspci). I even tried binding everything to pci-stub in the kernel options.

 

hmm didn't know about this.

 

What I have is:

 

PCI-E 16

PCI-E 1

PCI-E 16

PCI

 

Should I be ok with one x16 video card and then either one x1->x16 video card OR PCI video card?

 

If you only have one PCI slot then this shouldn't even be a concern. One bridge to one PCI slot means there really shouldn't be any effective difference. So you could install something in all the slots and pass each through to different vms. PCI-e devices communicate some kind of id so that the hypervisor can know which device to talk too. Whereas the PCI bus doesn't have anything like it so the hypervisor just sends communication to the entire bridge and can't split up devices behind that bridge to different VMs. That's my kind of crude understanding of why this limitation exists.

 

In theory a motherboard manufacturer could put multiple PCI bridges in for each PCI slot to get around this. In practice, they're never going to do that since it increases cost and is usually of no benefit.