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PCIE to USB expanders
tecsol1111bit last edited by tecsol1111bit
Has anyone used or know about the PCIE to USB port expanders, some look like just PCIE to USB expansion boards and other look like a break out card to PCIE 1X connections.
Has anyone played with or used any of these?https://forum.getpimp.org/assets/uploads/files/1518741324214-htb195fuxfym8kjjszfuq6af7fxax.jpgurl)
Can you link to the product itself? Also, just because it looks like a USB cable, does not mean its using USB protocol :)
Hard to make out, but my guess is you are looking at a PCIe switch. They use a switch, just like a network switch as an overly simple example, to split up the bandwidth to a single PCIe lane, into four new lanes. They are allowable with the PCIe 2 bus architecture, and there are are some cheap chips out there that implement the services.
The chipset on the motherboard you are using will also need to support addressing the additional lanes. So do your research on the chipset your MB uses, and how your MB BIOS enumerates the bus. Also be aware that you are not simply gaining ports, you are splitting traffic on a port. So figure your 5Gb port is capable of chunking data around at 625MB/s. Adding in this device will split that into four, and add in some overhead to keep track of it all. Figure each slot will only yield about 150MB/s max, and that is assuming a lot of things are perfect along the way.
How does this impact you? If you are mining ETH, when you build and populate the DAG, you will want to do it consecutively instead of concurrently for the GPUs attached to the switch. Be prepared for that phase to take at least 4x as long, if not 5x as long. And when shuffling that much data through yet another point of failure, be aware that you might get some faulty bits in play that do strange things to your results. So keep a close eye on rejects and the like.
I have used a Pericom PI7C9X bridge based PCIe switch with PIMP on an H110 based MB without issues.
Anything we can learn would be great, how does the install you're working with do? Much system impact?
The first one is a PCIe switch. Do not confuse it with the second one, which is a USB 3 adapter.
Again, just because the card manufacturer uses USB3 cables to extend the PCIe bus from the main IO card to each riser card, do not confuse it with a USB port. It is only using the cable because they are inexpensive, work well, and carry the required data at the speeds needed.
The first card listed, the PCIe switch, will work with PiMP just fine IF, big IF.. the MB chipset supports the number of total lanes deployed. You will also need to make sure you use at least PCIe 2 signaling to get support for the switch protocol. These settings are done in the BIOS, and not supported or provided by the PiMP team.
As an example, an H110 an support 6 PCIe slots. An H170 can support 16. A Z170 or H270 can support 20. And a Z270 is 24 max lanes. These are limitations of the chipset, not the physical count of slots on a motherboard. So do your homework first :)
As for system impact, it comes down to if the parts are quality bits. Counting on a twenty dollar part to traffic cop two thousand dollars worth of GPUs is a personal choice in the end. I used one to extend out a micro ATX H110 board I use for a testing rig only, and it was able to drive a couple more GPUs without stressing things. I did change my DAG loading to be sequential or consecutive. This changes my start up time, but reduces stress on the switch.
Good luck and keep us informed of your progress!
Anjin, excellent information, I'll have to be detailed in looking at the control chip.
Thanks very much for the insight and understanding!!!!
Paz last edited by
I am using one of these. I have not tested rigorously, but I so far has split a 1x lane PCIe into 2 of the possible 4 connectors. I have seen 16x lane splitting to 8 slots as well but not tried them. So far I have 10 GPUs on an Asrock H110. I dont need the splitter at all since the asrock supports up to 13 GPUs but I figured if I wanted to try and get to 16-20 GPUs on this rig, I would try out the splitter before I got that number. I dont have much to say other than I tried it and I'm watching to see if any of the nuggets of wisdom Anjin gave us.... So far it's working.
Thanks for the insight paz! What make is the splitter?
Paz last edited by
It was this
Hah, thats funny... A splitter implies 'splitting up a set of pipes into a higher number of sets of less pipes.' Like splitting a 16x to a pair of 8x. This is known as bifurcation in the PCIe world by the way, cause you can only split a set of pipes in half, then half again, etc.
And since you obviously are putting this into a 1x slot, and it gives you 4 - 1x slots, it is a switched bridge. Note the wee little chip there, most likely that same Pericom PI7C9X PCIe bridge chip I previously mentioned. Another term that might help source you a part is 'multiplier', a term that also implies a switched bridge.
Thanks guys!, I was back tracking that chip also!
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