Posts by Hiigaran
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1) Message boards : Number crunching : PCI-e Bandwidth Usage (Message 22616)
Posted 578 days ago by Hiigaran
I do plan on getting a new computer regardless, so I'm thinking I'll have one system primarily for personal use, and DC as a secondary function. I can test that with and without x1 risers.

If things do work, then I'll probably run one or two headless systems full of GPUs and access them via SSH on the first system. If not...well I guess I'll probably need to find a motherboard that supports x8/x8/x8 and build three systems.
2) Message boards : Number crunching : PCI-e Bandwidth Usage (Message 22613)
Posted 578 days ago by Hiigaran
That's all well and good, and there's some really good information here. However, you are referring to some outdated GPUs there. My original plan was to use a heap of GTX 1080s (expensive, but uses less than 190 watts peak), but given how much performance those cards have, x1 sounds like a limiting factor, even if it is 3.0.

I have no doubt that if someone wishes to use low-end or low mid-end cards, this will work just fine. I need to gather data from someone in possession of a flagship GPU to see if the limited bandwidth would hold out.
3) Message boards : Number crunching : PCI-e Bandwidth Usage (Message 22591)
Posted 582 days ago by Hiigaran
I could have the software wrong, though someone else originally reported using it apparently. I'm stuck on a 10 year old linux laptop, so I can't confirm. I definitely know that GPU-Z shows PCI-e bandwidth information, but I don't know if it reports it real time.
4) Message boards : Number crunching : PCI-e Bandwidth Usage (Message 22584)
Posted 583 days ago by Hiigaran
Copying this from the BOINC forums:

I've been having some discussions on several sites regarding GPUs and bandwidth usage for distributed-computing projects, and I wanted to broaden things by hopefully getting some BOINC experts in on the matter.

Now most of us are probably familiar with GPU mining and how hardware is generally deployed in these farms, but for anyone who isn't too familiar with it, a mining farm is typically comprised of a cheap motherboard with as many PCI-e slots of any size, some basic RAM, a cheap CPU, and of course, the GPUs. Due to space limitations, these GPUs are normally connected to the motherboard via a flexible riser which is an x1 adapter at the motherboard end, an x16 adapter on the GPU, and a USB 3.0 cable connecting the two to each other. Essentially, these are PCI-e x1 extension cables. They do not actually use a USB interface. a 3.0 cable is used simply because it has the right number of wires inside to map to an x1 interface.

Now, given that these risers are bottlenecked at x1 bandwidths, this would limit performance for high-bandwidth applications such as gaming, and significant performance reductions would be observed. Since cryptocurrency mining does not require high bandwidth, no performance loss occurs here, as x1 bandwidth on PCI-e 2.0 or 3.0 is never maxed out.

I had assumed that since mining does not require such high levels of bandwidth, perhaps distributed-computing projects might be the same. In the past few weeks, I've been discussing this over on the Folding@Home forums, and to my disappointment, anything less than PCI-e 3.0 x4 or PCI-e 2.0 x8 would result in bandwidth saturation, and thus a performance loss occurs due to the GPUs never reaching full load. This was rather disappointing for me, as I had wanted to build a system specced similarly to a mining rig, for the purposes of distributed-computing.

After a bit of thinking, I started to wonder if every project would require the same levels of bandwidth as F@H, so here I am. With the lengthy backstory out of the way, my question to you guys is simply this: Are there any GPU projects on the BOINC platform that do not saturate the PCI-e x1 interface?

I would love to get some data from anyone working on GPU projects. MSI Afterburner shows bus usage, so if a few people are willing to spend two or three minutes to take a few measurements, I would really appreciate it. Please let me know what size and version the PCI-e slot of your GPU is as well.

If anyone is able to help out with posting some data from their rigs, it would really help.

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