PCIE Bifurcation

MiniItx

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Jul 4, 2020
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Hi everyone, I'm working on a new build and I have one of c_payne's risers.

Here is the build I've been working on: https://www.overclock.net/forum/180...0890-new-build-lian-li-pc-tu100-mini-itx.html (account was pending approval here or I would've maybe thread on this site instead)

I got the bifurcation working!! I booted up the PC and the GPU on the riser was used as the display by default :D I have to install Windows now.

Ran into some issues troubleshooting, I think one of my PCIE extension cables malfunctioned so I couldn't tell what was wrong initially, replacing it got everything working.

I'm not in the clear just yet but real excited to have it working at this stage in the configuration
 
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MiniItx

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Joined
Jul 4, 2020
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Hi everyone, I'm working on a new build and I have one of c_payne's risers.

Here is the build I've been working on: https://www.overclock.net/forum/180...0890-new-build-lian-li-pc-tu100-mini-itx.html (account was pending approval here or I would've maybe thread on this site instead)

I got the bifurcation working!! I booted up the PC and the GPU on the riser was used as the display by default :D I have to install Windows now.

Ran into some issues troubleshooting, I think one of my PCIE extension cables malfunctioned so I couldn't tell what was wrong initially, replacing it got everything working.

I'm not in the clear just yet but real excited to have it working at this stage in the configuration
I GOT IT FULLY WORKING! :D

Elgato HD60 Game Capture PRO + NVIDEA Quadro P2000 Works with THIS BIFURCATION RISER using the ASUS ROG Strix Z390-I Mini ITX Motherboard with Windows 10 Pro 64bit

The Elgato Game Capture software detected the card and it works connected via HDMI to my video camera.

I didn't have to do much tweaking to get it to work but had to troubleshoot things like faulty cables.
 

MiniItx

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Jul 4, 2020
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Can this board work with a Asus hyper x16 with 4x 2tb nvme drive's?

I think it would, only bit of additional info I can offer is the thread here: https://www.reddit.com/r/sffpc/comments/dg55gt/asus_strix_z390i_bifurcation_possible_x4_x4_x8/
Like the thread mentioned I enabled hyper m.2x16 in BIOS for the bifurcation. Tbh I just did that because the redditor did, I assumed that enabled the bifurcation.

Also with my bifurcation card in, with the GPU in the slot farthest from the PCIE connector, here is what appeared under my GPU POST in the BIOS. This boot screen came from the GPU on the Bifurcation card also not the onboard motherboard GPU

IMG_1734.jpeg
The dropdown for the Bus Interface only gave one option the option of 'Unsupported Slot'

If my GPU were attached without the bifurcation and 2nd GPU (the capture card I used) the BIOS would instead just display the GPU name and details, as you would expect.
 
Joined
Jul 22, 2020
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I am using an old sandybridge mobile cpu and mini itx industrial motherboard for an unraid server. It only has one x16 pcie slot. Since its an old motherboard, it does not support bifurcation. I am using a modern asmedia 2824 based pcie switch card so I can run a gpu and an lsi hba off that single slot. But its a tad bit expensive ($150) just to split that pcie slot. Btw for anyone that is trying to get bifurcation on an old motherboard that doesn't support it, you can use those m.2 raid bifurcation switches (like the asm2824) along with m2 to pcie risers and they work great.

I puchased one of these old sun/oracle pcie switch riser that have pcie switch chips for a measly $10. Its for sun/oracle x4250 x4270 westmere era xeon servers. Its using an IDT 89HPES24T6G2 pcie switch chip, which is only pcie 2.0. But since my cpu is sandybridge, thats good enough for me.

Problem is when I install this, the system won't boot. The motherboard standby light turns off and even the PSU (with PS_ON bridged connection) turns off. So what I think is going on is circuit protection is being enabled, telling me that the pcie pinout on this is non standard. I saw that supermicro pcie risers also have non-standard pcie pinouts.

I can't find a pin out diagram on anything related to sun/oracle pcie risers. Does anyone happen to know where I can find that, or perhaps if there is some trick to getting to these to work, like taping certain pins. Thanks.
 

maeslin

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Apr 24, 2020
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telling me that the pcie pinout on this is non standard.

Eyeballing it, that's not just a non-standard pcie pinout, that's not a pcie connector at all. The 'short' stub is the wrong way around and in normal pcie it should be mainly carrying 12V, while the two extra wide power traces at positions 20-21 and 24-25 are where some of the pcie data lanes would normally be. It's possible it might have damaged the pcie lane drivers on your motherboard in the process.
 
Joined
Jul 22, 2020
Messages
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Eyeballing it, that's not just a non-standard pcie pinout, that's not a pcie connector at all. The 'short' stub is the wrong way around and in normal pcie it should be mainly carrying 12V, while the two extra wide power traces at positions 20-21 and 24-25 are where some of the pcie data lanes would normally be. It's possible it might have damaged the pcie lane drivers on your motherboard in the process.

Yea I thought it was weird there are the double traces there. The flipped orientation of the pcie traces, I was hoping it was just by design for their custom server/motherboard but that it still follows standard pcie. I found the specsheet for a reference card by IDT for this pcie switch chipset, and its odd that they listed side B pins for side A and vice versa. They also stated this follows standard pcie specifications. The time spent to make a pcie adapter that flips side A and B pins wouldn't be worth it, and it still could not be the solution. Luckily it didnt damage either motherboard I tried it on. If I taped the 3.3v traces, the mobo standby light would stay on but it still didnt boot.
 
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jlscott3

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Aug 27, 2020
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Hi all- I haven't built a PC in about 10 years, but it's time for an SFF rig and I'm trying to come up to speed on bifurcation. I'm planning a build in a Sliger SM580 based on the ASRock Phantom Gaming B550 ITX/ax motherboard and a Sapphire Pulse 5600XT, both of which support PCIe 4.0. The motherboard allegedly supports bifurcation in UEFI. The 5600XT is a 2.3 slot card, which should fit in the 580 and leave the near slot open. I would like to add 10GbE at some point, which requires a second PCIe slot. Most of the available 10GbE NICs seem to be PCIe 3.0. I'm a little confused as to whether I could mix PCIe generations on a bifurcation cable. Is that possible? Anybody get bifurcation working with this mobo/graphics card combo?

Sliger sales says that their bifurcation cable is rated for PCIe 3.0 only, but I think I saw earlier posts in this thread that said people have it working with PCIe 4.0 components. I figure I might roll the dice on that and replace it with a LINK UP cable and c_payne riser if it doesn't work.

I'm aware of the ASRock X570 Phantom Gaming ITX/TB3, and I could use the TB3 port + a TB3 to 10GbE adapter to add 10GbE. However, I'm turned off by some of the compromises that board makes, and I'd like 2 M.2 slots.
 

ChronoDog

Weaksauce
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Oct 15, 2009
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111
A new option in the latest BIOS (2.60) for the ASRock X570-ITX/TB3 apparently adds x8x4x4 and x4x4x8 bifurcation support:

200905130029.jpg


The x4x4x4x4 option seems to be gone, though.
 
Joined
Sep 5, 2020
Messages
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My first post so hello everyone!

Does anyone know if there are any Threadripper 3 motherboard that support 16x -> 8x8x bifurcation? I'm looking to put dual GPUs in two 16x slots for total of 6 GPUs. I have checked Asus, Gigabyte, ASrock and MSI user manuals, but they either not mention it, or only mention 16x -> 4x4x4x4 (which might be sufficient for my use case, but would prefer 8x8x).

Alternatively, do you know any recent Intel motherboard which would support 16x -> 8x8x and CPU with 64 pci lanes or more?

Thanks!
 

Badrig

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Jul 5, 2020
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Hej!

I have an ASRock Rack E3C236D2I, that supports PCIe Bifurcation x8x8 and x8x4x4 - so far no problem.
But the Riser from Quanta I used doesn't seem to work. Perhaps it not universally compatible.(see the attached image)
I already tried all 4 possible jumper settings, but the result is the same: Only the card in the lower slot works - regardless which card is insert.
IMG_20200703_163042-2.jpg
Quanta does not reply to my requests, the seller rejects my complaint.
Any idea where to find a working riser card?

My case is an Inter-Tech 1.5U-1528L, my setup should become a router. Some impressions:
1600502901656.png1600502866502.png

PS: Both cards and both smaller risers are tested and working.

Thanks!
 

Badrig

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Jul 5, 2020
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60 Euro is a bit much for a try. Will you give me the opportunity to return it? Thanks
 

Dagarath

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Oct 2, 2020
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Hello everyone, I have been reading through quite a bit of this thread and I must say it is quite amazing how much data has been amassed in one place with respect to bifurcation. This motherboard Gigabyte X570 UD
appears by specification to be capable of, through bifurcation and m.2 key to pcie riser, of up to 13 4x pcie 3 slots (4 would potentially be pcie 4).

Am I simply reading the specifications wrong?

I'll likely contact Gigabyte myself as that seems like insanity for a consumer board at this price.
 

C_Payne

Limp Gawd
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Jan 6, 2017
Messages
156
Hello everyone, I have been reading through quite a bit of this thread and I must say it is quite amazing how much data has been amassed in one place with respect to bifurcation. This motherboard Gigabyte X570 UD
appears by specification to be capable of, through bifurcation and m.2 key to pcie riser, of up to 13 4x pcie 3 slots (4 would potentially be pcie 4).

Am I simply reading the specifications wrong?

I'll likely contact Gigabyte myself as that seems like insanity for a consumer board at this price.
Yes that is a misinterpretion of the specs.
Slot 1 are 16 CPU lanes that could if bios support would be there support x4x4x4x4
The other two x16 slots are chipset lanes each running at x4
Add the nvme you are at 7 x4 devices.
 

Dagarath

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Oct 2, 2020
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Yes that is a misinterpretion of the specs.
Slot 1 are 16 CPU lanes that could if bios support would be there support x4x4x4x4
The other two x16 slots are chipset lanes each running at x4
Add the nvme you are at 7 x4 devices.

Ok thank you very much, most boards I've looked at the specs are very explicit, even stating how they can be split. 7 is not too bad I suppose if I am stacking a bunch of x4 nvme pcie adapters in there, with the onboard nvme as well.
 
Joined
Feb 25, 2019
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Has anyone here tried the 3M 500mm riser cable for PCIe 4.0?
I'm planning a new build where I would need 2 of them, I'm wondering if it will work.
 

Badrig

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Jul 5, 2020
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Try this one:
https://peine-braun.net/shop/index.php?route=product/product&path=65_59&product_id=68

The cards will sit a bit lower, but by taking a brief look at your case that shouldn't be an issue.
"a bit lower" :ROFLMAO:

well...
I will try to "fix" this with a flexible x4 extension, which I have to order and wait about 4 weeks for. I hope that you would still take the card back if I can't get it fit properly. At least this one works in contrast to the old one.
I cannot understand why there are these mainboards and such cases, but no matching risers.
1605709930282.png


I consider if this one would be more useful, because if I have to work with flexible extensions anyway, I could save the M.2 adapter.
https://peine-braun.net/shop/index.php?route=product/product&path=65_61&product_id=104
 
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maeslin

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Apr 24, 2020
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313504_5eY4pfv.jpg

C_Payne by any chance, would you happen to have already designed an x8/x4/x4 low-profile adapter? Something like your earlier x4/x4 attempt but with an m.2 slot on either side of the PCB (or a 'double stack' m.2) and the x8 'inline' slot at the top?

Unfortunately the x8/x4/x4 variant on your site with the 'x8' mounted on the side wouldn't fit in this specific case.

An x8/x4 could work as well, basically the old 'x4/x4' low profile design but with 8 lanes reaching the top connector.


It would be amazing to have one or two nvme drives and a low-profile 40gbe or sas2 card share an x16 slot.
 
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mshiels

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Dec 1, 2020
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Does anyone have a list of decent quality X16 or X8 riser extenders that just extend your slot - either to fit a low profile into full profile or just get a slight height increase? I see alot around but wonder about quality!! I am trying to figure out how to effectively use all my slots in a SuperMicro X9DR3-F board, which as far as I can tell does Bifurcation etc, but in some cases I just need to lift a card out of the way of a ADT cable in the slot beside it. I am running a number of LSI 9285CV-8E cards which run super hot, so I have added tiny fans to the heat sinks, but now the 1 slot becomes a 2 slot card, not good for slot usage. I am pretty sure I'll getting some C_Payne items along with extenders and some very short ADT-Link cables. The 16->8x8 Low_Profile_x8x8_rev2 with a ADT R33UL 5CM looks really compact!! (R33UR rolls back on itself so not quite as clean).
 
Joined
Nov 20, 2017
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C_Payne What would it take to get something like the dan-case/ghost bifurcation adapter but with the slots switched, my motherboard doesn't support configuring which slot is primary.
(https://peine-braun.net/shop/index.php?route=product/product&path=65_59&product_id=87)

Should I just open an order for a custom PCB?

I have a vfio (gpu passthru set up) The more powerful card which I use for the host is watercooled and single slot, but because of the slot ordering (which my bios wont let me change) my bios keeps outputting on my weaker card (not single slot) that isn't hooked up to an actual display as it has a dummy plug and is interacted with through remote desktop and looking-glass.
 

C_Payne

Limp Gawd
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Jan 6, 2017
Messages
156
That will be a tough design work, imagine all the traces crossing each other.. may even need 6 layers for that.

I am sure you can solve it in software!

Please disable CSM in BIOS! Legacy VGA is limited to 1 card. UEFI GOP can handle multiple outputs. You may be able to configure the active output in your BIOS or with an UEFI shell option. Since you are passing the second card through I take it maybe get rid of the option rom for the small card, and only load it with your virtual machine.
 
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Nov 20, 2017
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I'll look through the bios again.

This isn't a big deal for the OS, I just load the vfio driver for the card I don't want and OS just acts like it isn't there. The bios really wants to use that card though, and it thinks there is a monitor because of the dummy plug. I guess whenever I need to access the bios I'll have to do a cable swap :(
 

C_Payne

Limp Gawd
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Jan 6, 2017
Messages
156
I'll look through the bios again.

This isn't a big deal for the OS, I just load the vfio driver for the card I don't want and OS just acts like it isn't there. The bios really wants to use that card though, and it thinks there is a monitor because of the dummy plug. I guess whenever I need to access the bios I'll have to do a cable swap :(

Try flashing an empty BIOS to the card (after backup ofc!) you can then load the bios through your virtualization software. (or try removing the UEFI GOP)
Alternatively, play around with the UEFI shell. I know it's possible to add a driver to be loaded. Maybe you can blacklist or remove it there.
 
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Oct 31, 2019
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Is anyone using @C_Payne’s ncase m1 bifurcator with a low-profile GPU? I’ve searched through the forums and most seem to want other cards like sound cards or 10G networking.
 

maeslin

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Apr 24, 2020
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Quick question I haven't found an answer to yet. On a bifurcated bus, do all the lanes have to be at the same speed or does it negotiate them independently?

(ex. in x8/x4/x4, with a pcie 2.0 x8 card and a pair of pcie 3.0 x4 cards, will it run everything at pcie 2.0 speeds?)
 

C_Payne

Limp Gawd
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Jan 6, 2017
Messages
156
Quick question I haven't found an answer to yet. On a bifurcated bus, do all the lanes have to be at the same speed or does it negotiate them independently?

(ex. in x8/x4/x4, with a pcie 2.0 x8 card and a pair of pcie 3.0 x4 cards, will it run everything at pcie 2.0 speeds?)
Individual ports will negotiate individual link bandwidth. a mix of gen2/3 is very well possible.
Some weird BIOS may screw this up but I haven't seen any.
 

walterd53

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Jan 20, 2021
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I can report another success using a c_payne x8x8 riser on an ASRock B450-ITX/ac.
Any BIOS version above 3.20 didnt work with bifurcation but I got version 3.76 from asrock support which works fine and I don't need to patch my kernel to pass through one of the GPUs to a VM (There is a bug in AGESA versions <1.0.0.4 B).
Apparently there was an issue with the later AGESA versions where they do not support bifurcation on Pinnacle/Summit Ridge. I can upload this for anyone who wants it.

I originally tried using a bifurcation riser from taobao here but got no output on any card through the riser, even with only one slot populated. As far as I can tell it's a dud.
All the pcie pins are routed correctly so I can only assume it's the clock buffer or a signal integrity issue but I lack any equipment to test it further.
Do you still happen to have that BIOS version on hand? I am also attempting bifurcation on the ASRock B450-ITX with a Summit Ridge CPU, but it doesn't work on the BIOS version 3.70 for the motherboard. It does work on 4.10, but I am also trying to pass a GPU to a virtual machine as well. That version appears to have removed the option that would (hopefully) allow me to avoid having to perform the kernel patch.
 

DanaG

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Aug 3, 2006
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29
I have an interesting idea for a bifurcation riser: something to allow putting an Optane H10 SSD in a standard machine. That drive is an M.2 device where the x4 slot is bifurcated into two x2 slots. Most mainboards don't support bifurcation to x2, so this riser would have to take an x8 slot and bifurcate it into two x4 slots, then throw away half of each.

Alternately, an M.2 passthrough adapter that allows you to at least select which half of the Optane drive to expose, would be useful too. When I tried my drive in an AMD system (x570), it only showed the Optane, and in an Intel (Supermicro X10, C224) system, it showed only the flash. It would be nice to be able to choose one or the other intentionally.
 
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Feb 3, 2021
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Hi all,
As much as I have searched the internet, I have only found this wonderful space where perhaps you can help me.

Currently I have to mount a streaming pc on a NCase M1 with a 3900x, an asus b550i and a rtx 2060 2 gigabyte with slot ..

As I have space I can place a pci e elgato x4 capturer.
I see in the post
https://peine-braun.net/shop/index.php?route=product/product&path=65_59&product_id=77

and I think it can help me, however, I do not understand how I can place it inside the Ncase.

It would be wise to fit it into the pci of the motherboard and in the first slot a low profile card (elgato capture)
and in the slot below through a riser add the graphic?

if so, where is it screwed? Do you need any extra modification, add resistors or something similar?
I am not a handyman with electronics if I had to do something, I already discard the idea of buying that product.
or just buy it, plug it into the sata connection and put it as indicated above.

I have also seen the possibility of using the m2 on the back with a x4 adapter cable and plugging the capturer there, however, I don't know which is better and that it will give me less problems.


As a last option it will be to switch to atx, but I am in love with this case..

Thanks for your attention and sorry with my non-native English.

edit C_Payne ?? Can u help me?
 
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C_Payne

Limp Gawd
Joined
Jan 6, 2017
Messages
156
sorry for the delay in response.

It would be wise to fit it into the pci of the motherboard and in the first slot a low profile card (elgato capture)
and in the slot below through a riser add the graphic?

yep that's the general idea.
The GPU will need some support. Ideally you would mount the riser cable with some custom made pieces to the chassis.
No electrical modifications neccessary on the PCB, but of course you would have to think of a way to properly mount the gpu.

C.
 

Furious Nerd

2[H]4U
Joined
Sep 14, 2006
Messages
3,194
Just called gigabyte... whomever I spoke with hadn't heard of PCI-E bifurcation before and said that it won't work. I believe this.

Somehow I feel cheated of this excellent feature of the Z97 chipset&#8211;&#8211; should have anticipated this desire a year ago.
My Gigabyte B550i Aorus Pro AX has a bifurcation mode toggle in the BIOS =/

edit: jebaited by a necro thread, sorry.
 

Mosquito

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Feb 9, 2020
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7
Good to see things still chugging along here. We are fortunate to have C_Payne in this community, 100%.

Has anyone tried using Davinci Resolve with Bifurcated GPUs by chance? I've got one of C_Payne's cards and it's working rather well, though windows GPU-Z reports some oddities, such as one card being x4 and the other being x1, which I don't really believe (BIOS is set for x8x8)... Aside from that, the results are pretty good in TimeSpy. Almost 75% increase in just GPU score running both instead of one.

However, when running Davinci Resolve Studio, I was seeing faster render times with the single GPU than I was the dual GPU setup. I have a feeling Resolve accesses the GPUs more directly, or in a way that gaming/benchmarks just don't seem to. Also, if I run a Furmark full screen stress test/benchmark, it'll usually lock up on me right away.

I do have a youtube playlist documenting this build, with much of this information coming up in the next one, if anyone were interested:
Jam Packed - InWin A1 Mod

Single GPU with just the PCIe Riser: 6,610 GPU score with my Vega 56 (Sapphire Vega Pulse/Nano, watercooled, stock clocks)

02.09.21_12.04.22_Single%20GPU%20Timespy.png

Dual GPU using the C_Payne card: 11,459 with both Vega 56's on stock clocks

02.09.21_12.04.29_Dual%20GPU%20Timespy.png
 

Kabachi

n00b
Joined
Feb 16, 2021
Messages
4
I just found this thread and also C_Payne splitters on eBay. I ordered one just to experiment, and I got a few questions:
1) I see something that looks like a power connectors on the pictures. Does this mean they can provide additional power to the cards? I really want to use it with two 50w cards connected to each slot.
2) If I use that splitter on a slot that is x16 mechanically but motherboard makes it x8 because it does not have enough pcie lanes, would I get x4 + x4 split?
 
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