A way to connect multiple GPUs via usb?

ScioMind

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May 28, 2014
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Not sure if this is possible, or has been done before....

Is it possible (perhaps using some sort of multi-GPU adaptor, or something to that effect) to connect multiple GPUs to a computer via USB? This would allow one to connect some number of GPUs to a machine (maybe even a laptop) and mine from them. I suppose that using a USB hub, it might even be possible to add more and more GPUs over time.

In this way, one could essentially "start small" but add more GPUs (and hashing power over time).
 
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tboy32

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Jun 24, 2014
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Pericom makes a USB 3.0 to PCIe bridge chip. It can be configured to provide two single lane slots or one 2-lane slot. Unfortunately it uses a staggered pin arrangement requiring expensive PCB manufacturing techniques (such as laser-drilled microvias). I'm pretty sure that's the only company that sells a USB to PCIe product like that.

Back in Jan/Feb I designed a board using this chip which used one 8-pin PCIe power connector (12VDC in) and provided two single-lane PCIe slots spaced to accomodate two double-wide GPUs with about 1cm air gap in-between. Long story short, I never had it manufactured due to the high cost of manufacturing.

Google "pci-e-express-1x-to-4-port-pcie-1x-riser-switch-card-with-usb-3-0" for another solution (although doesn't use USB protocol - just the physical cable).
 

ScioMind

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fra55: Here's what I envision - The computer (even a laptop) could be used for the "getwork" aspect, and could then forward the relevant information to the GPUs via the USB cable. The GPU's could be powered by some auxiliary power source, other than the USB. The GPUs would do the hashing, and send the results back to the computer, through the USB cable.

tboy32: Based upon your google search suggestion I found this: http://www.bplus.com.tw/Adapter/USB3380EVB.html
So...would it be possible to connect a USB cable between a spare laptop (for example) and the USB 3380, connect a "PCI riser" (I think that's what it's called - basically something that converts one pci port into many) to the USB 3380, and then connect several PCIe cards to the riser? And then start hashing away?

I am thinking this should be much more economical that building a mining rig from scratch (since I already have a spare pc laptop, and even an older spare mac desktop which I don't use for much), so it would just be the cost of the USB 3380, the PCI riser (if that's what it's called) and the GPUs. A second benefit would be that most of the heat generated would be in the GPUs, located external to the computer (either desktop or laptop) so any overheating shouldn't fry the computer itself, but only one of the GPUs

I'm somewhat new to this, and trying to figure out the best way for me to go in terms of setting up a really good rig (for darkcoin) with the minimal initial expense, but with a large potential for future expansion.

And to both fra55 and tboy32, thanks for taking the time to answer.
 
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tboy32

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Yes, that product uses the chip I was referencing (I thought it was Pericom, but it is indeed PLX). You could add a PCIe lane to your laptop by plugging it into a USB 3.0 port on your computer. Then you could plug in a GPU and start hashing. You'd need some adapters (like a female-to-female PCIe slot adapter), but it looks like you could theoretically do it.

Looks like that board is $65 and will get you from your laptop (must have USB 3.0) to one PCIe slot (lane). For expansion, you could then use something like the "PCI-E express 1X to 4port PCIe 1X riser switch multiple card with USB 3.0 cable" from Sintech Electronics (sorry, I can't post links until after this post). You'd plug that into the single slot from the USB 3380 and it would split it into four slots that you could then use four USB risers on to plug in four GPUs. You might be able to "tree" out using multiple splitters to get even more GPUs off of a single PCIe lane, but I've never read of anyone attempting this so you'd have to try it out to see if it works.

Of course you'll have to figure out a custom power supply system because, as fra55 pointed out, USB can't handle powering a GPU. USB riser cables usually have standard 4-pin peripheral connectors that make it relatively simple to set up.
 

ScioMind

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Ideally, I'd like the GPU to be an NVIDIA GeForce GTX 750 Ti, but the riser you suggested unfortunately does not support that card. I wonder why? I initially would have thought any GPU would have been supported. Perhaps this is because of the power requirements? Or something else?
I think if someone could make.something like this work it would.definitely catch on...but it should be able to utilize the fastest GPUs available.
 

tboy32

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I don't think I remember reading anything about it being incompatible with certain cards. I'm pretty sure your initial thought was correct - that the risers should work with any GPU. Could you link me to the place that says that so I can check details?
 

ScioMind

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Check the following page...it is at the end of the "Features" section:
http://www.aliexpress.com/store/pro...-cable-for-diy-bitcoin/825827_1444567810.html

Also on this page, at the end of the "Features and Specifications" section:
http://www.aliexpress.com/store/pro...-cable-for-diy-bitcoin/825827_1444567810.html

Oddly, when I go to the actual Sintech page for the product, there is no such note, although the page seems broken:
http://www.sintech.cn/riser card/ST-PCIE4PCIE PCI-E X1 to 4 PCIe x1 riser cable.html

Upon reflection, I am wondering if the problem is simply the size of the NVIDIA GeForce GTX 750 Ti, rather than the power or something else. Perhaps it is simply too big/thick to put two of these NVIDIA cards side by side on this?
 

ourlink

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Have you searched YouTube? I vaguely remember watching a video a few months ago where the user had configured a set of 3 GPU's running off of USB risers. I can't remember if the USB risers were plugged into the MB directly or if they were plugged into a USB Hub.

Look up Bits B' Trippin as I think that was the user that had the video posted.
 

ScioMind

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Have you searched YouTube? I vaguely remember watching a video a few months ago where the user had configured a set of 3 GPU's running off of USB risers. I can't remember if the USB risers were plugged into the MB directly or if they were plugged into a USB Hub.

Look up Bits B' Trippin as I think that was the user that had the video posted.
I have seen the method where the USB risers were plugged directly into the motherboard before. This definitely works, but would be unusable for a laptop (of which there are three at my place) or for the iMac I have. I really would love to be able to find a usb solution, as it would allow one to use a very wide variety of machines for mining, and would not require modifying one's desktop for the purpose.

While on the subject, I think I have only found USB 3.0 to PCIe adaptors, but I am not sure if USB 3.0 is actually required, or I a USB 2.0 port on the computer would still do the job. (I don't think one would need especially fast data transfer between the computer and the GPUs, so it seems that 2.0 should suffice.) This would allow for an even greater number of computers to be used.
Imagine how nice it would be if, regardless of your computer, as long as you have the needed usb port (as pretty much all computers do have usb) all you would need to do is buy a few parts, plug them together, connect via usb, and you're up and mining! That's my goal...I know it should be possible, but I am just trying to figure out the best way...and don't want to but parts that won't actually do the job.

I do appreciate everyone who is offering suggestions. Hopefully we'll get there sooner rather than later!
 

tboy32

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Jun 24, 2014
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One thing I have to set straight: USB riser cables such as this:

do NOT use USB signals. You CANNOT plug them into a standard USB port on your computer - it won't work. These boards use USB 3.0 cables and connectors because USB 3.0 cables are spec'd for nearly the same electrical signaling going on in one lane of PCIe. Also, USB cables are commonly made. There is no USB signal going on with a USB riser. You can even find risers that use SATA cables instead (again, similar electrical signals, but NOT the same).

The little 'dongle' connector in the top right of that picture must connect to a PCIe slot on your motherboard. I understand that laptops don't have those (although some have mini PCIe slots for things like wifi cards - and adapters are made to convert from mini PCIe to a single lane PCIe slot), and I agree that it would be nice to have a solution that DOES use USB 3.0 (which most laptops have).

That being said, the USB 3380 board you found earlier should work to bridge USB 3.0 into PCIe. If you watched the video on that page, the guy shows that he plugs a video card into the adapter board, and then from the adapter board into a USB 3.0 port on that laptop, and it works. That USB 3380 chip/board is the key to this process - it will convert the USB 3.0 signals to/from PCIe signals.

The issue with that USB 3380 is that it has 'reverse' connections. You'd need a male-male USB 3.0 cable (like the ones that come with USB risers in the pic above), as well as a female mini-PCIe to single lane PCIe slot adapter (which probably exist but I haven't looked yet). This would work for a single GPU.

For expansion (up to 4 GPUs) you could then use that 4-way splitter product to plug the small 'dongle' board into the USB 3380. Then you have four single-lane PCIe slots available. You'd use four standard USb risers (like the pic above) to then split off to four separate GPUs. You wouldn't be mounting the video card right onto the splitter board. You may even be able to use, say, 5 total splitter boards to get 16 GPUs off of a single USB 3.0 port (although I think most OS'es only support up to 8 GPUs). You may also run into bandwidth limits when 16 cards are using a single lane of PCIe. You'd have to test it to find out.

I'd like to ask the place that sells the splitter what exactly causes it to be incompatible with that card. All mining GPUs that I've ever heard of use standard PCIe slot connectors, and thus use standard PCIe signaling. So I'm not sure exactly why they would say the board is incompatible.

I might just pick up one of those USB 3380 boards and try this out myself. I've been interested in a solution to this problem for a while now too so it'd be nice to figure it out.
 
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ScioMind

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tboy32: If I am understanding you, normally you cannot go from USB to PCIe, but using the USB 3380 card you can...and you would not need the "dongle" which you referred to either.

At that point I should be able to plug in a single GPU (still wondering about that NVIDIA card) directly into the 3380, or I could go further and set up PCIe risers/splitters if I wanted to add more GPUs.

I am getting it so far?

Also would it be entirely necessary to have a USB 3.0 port on the computer/laptop, or would USB 2.0 also suffice, albeit at a slower communication rate between the computer and GPU(s)?
 

fra55

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Well the USB device isn't plugged in the PC's ports...it connects the riser to the PCI Express slot
 

tboy32

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One of the images from the USB 3380 product page:

That's how you'd set it up for a single video card. That extra board (green-colored in the image) unfortunately costs an extra $100. You might be able to find a cheaper solution. All you really need is an adapter that goes from female mini PCIe to female single-lane PCIe (what the blue arrow in that image points to).

I stitched together an image for further explanation:

Please excuse the poor editing quality - I just threw it together. But you get the point :). I am pretty sure you need it to be a USB 3.0 port on the laptop.
 
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ScioMind

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@tboy: Thanks a lot! Don't worry about the editing quality...a pic is worth 1000 words! I really think I get it now. I.guess my last step before spending money is to see if I can find out why the NVIDIA card isn't compatible with that splitter mentioned a couple of posts up. I am hoping it's just the physical size of the gpu.
 

henry Velasquez

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Good day

I Live Colombia country , I am interested in a project with the manufacturer Dell in my region, to work with video cards to external high performance laptops, (EGPU).

Currently we have some models that offer web and using software (DIY) has been able to operate these components.

We need your support to validate whether creating a 16x PCIe to USB 3.0 adapter is possible for reason to plug and play with Express cards or equipment.

We look forward to your comments.


greetings
 

ScioMind

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May 28, 2014
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Good day

I Live Colombia country , I am interested in a project with the manufacturer Dell in my region, to work with video cards to external high performance laptops, (EGPU).

Currently we have some models that offer web and using software (DIY) has been able to operate these components.

We need your support to validate whether creating a 16x PCIe to USB 3.0 adapter is possible for reason to plug and play with Express cards or equipment.

We look forward to your comments.


greetings
For now (and probably forever, but you never know) I have abandoned the idea of connecting video cards via usb. It does seem that it is technically possible, provided that the laptop in question has advanced enough hardware already. (In particular it would need to have at least one USB 3.0 port...and possibly other hardware requirements.) It turned out that I simply didn't have a suitable laptop, or even old desktop, which would have been adequate for this project. I finally broke down and simply purchased a suitable computer, with the graphics card installed normally.