1 Motherboard, 8 GPUs -- PCIe Splitter?
#1
Question 
Hi all,

I have a single motherboard which has 4 PCIe x16 and 1 PCIe x1 slots. I have 8 HD7950 GPUs. I've looked into splitters a bit, and found this: http://www.amfeltec.com/products/x1pcie-splitter3.php

Though, I am unsure as to how the PCIe x1 will properly connect to the PCIe x16 connector. According to this article: http://champagneandsecurity.wordpress.co...w-q1-2012/ and here: http://blog.zorinaq.com/?e=42 , it is possible to connect it.

Can anyone weigh-in on my question? I have 1 motherboard, and 8 GPUs. How can I make all of them connect on the single motherboard?

Thanks!
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#2
Hmm. I think that many people would be curious to know if these splitters would work. Connecting the gpus will be one thing, getting them properly recognized by the OS might be an issue but I am not an expert in this. The other issue would be the power that they would be drawing from the motherboard or the effect on the GPU if they can't have that power from the motherboard. I will be following this thread to see what the experts say about them.
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#3
You don't need the full x16 lane. x1 is all that is used anyway, however, I don't know how the driver will treat 3 devices per lane... you might just have to get it and see what happens.

I should also say that you will most likely see longer than average loading times for wordlists since you will be tripling the work over a x1 lane.
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#4
As a heads-up to complete the life of this thread, I wound up getting two motherboards and am using VCL to connect them together. Though, as it can be seen in my newest thread, there are issues with that as well.
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#5
Sorry for the late reply here, don't check this forum very often.

Yes, we have connected 8 graphics cards to one machine using two PCIe slots and two of those splitters linked in the first post.

We have done this with first with Nvidia (gtx580) and then with ATI (HD 7970) cards.

To achieve this we used a frame to hold the cards and two 1200W power supplies to power four cards each, plus a 1500W supply for the motherboard. The big power supply on the motherboard was needed for the Nvidia cards, but is not needed for the ATI cards. We just changed the main PC to one with a 1200W supply, which is proving to be sufficient power wise (for some reason the Nvidia cards pulled more power through the motherboard vs the dedicated power supplies than the ATI cards do). The PC is in a tower case and sits next to the frame with its side cover off. The cables from the splitters/motherboard to the graphics card frame just hang in the air between the frame and case. The dedicated power supplies have the motherboard control cables shorted using a small insulated wire to simulate the "On" signal from the motherboard, and the onboard power switch on the power supplies is used to turn them on/off. You need to power up the graphics cards via the dedicated power supplies before turning on the PC. There is copious electrical tape used for insulation, including on the small boards that sit in the middle of the splitter cables - it looks dodgy as Hell, but its functional.

The frame holding the cards has its own cooling - a pedestal fan attached to the frame. This has been relatively stable for over a year, although we are now having GPU overheating issues as the newer PC with upgraded motherboard that I added yesterday is pushing the GPU utilization slightly higher than the last one, which is apparently just over the threshold of what it can handle. I'm confident I can get this sorted - perhaps by upgrading the fan or by moving some things around to improve airflow.

Im running Ubuntu Linux 12.04 for the OS. Driver wise you just need to run aticonfig to configure the use of all cards for ATI. Nvidia just worked. Very simple.

I posted some performance stats elsewhere on this forum (check my post history) if you are interested. Feel free to ask me if you have more questions.
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#6
So how much one splitter cost?
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#7
(11-13-2013, 08:01 AM)KT819GM Wrote: So how much one splitter cost?

The 4 way splitters were somewhere a little under $200 US each if I recall correctly. We bought them last year though, so prices may have changed,
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