How can it be possible to connect 4 PCI-e/GPU to 1 PCI-e Slot?

[Battousai01]

Hi guys, I am so surprised to see a PCI-e riser adapter that can connect up to 4 PCI-e cards into one PCI-e slot.

Here is what it looked like:

I have seen several YouTube videos of people using that adapter and I am so surprised to see that the set-up worked, the GPUs connected through the adapter are detected in Windows and are fully working.

So basically, my questions are:

1. How does this work? How can one PCI-e slot be used to connect multiple GPUs?
2. Is the performance of the cards connected to this adapter the same as if it is connected into a dedicated PCi-e slot?
3. Can this be used for ITX boards with only one PCI-e slot then use the board for mining or gaming?
4. What is the purpose of this kind of set-up aside from cryptocurrency mining? Can this set-up be used for gaming?

 

[Rifter]

Hi guys, I am so surprised to see a PCI-e riser adapter that can connect up to 4 PCI-e cards into one PCI-e slot.

Here is what it looked like:

I have seen several YouTube videos of people using that adapter and I am so surprised to see that the set-up worked, the GPUs connected through the adapter are detected in Windows and are fully working.

So basically, my questions are:

1. How does this work? How can one PCI-e slot be used to connect multiple GPUs?
2. Is the performance of the cards connected to this adapter the same as if it is connected into a dedicated PCi-e slot?
3. Can this be used for ITX boards with only one PCI-e slot then use the board for mining or gaming?
4. What is the purpose of this kind of set-up aside from cryptocurrency mining? Can this set-up be used for gaming?

1. Yes it works
2. They split the bandwidth
3. Yes
4. Its mainly for mining, could be used for gaming though but with the lack of SLI/CF support lately i dont see the point.

 

[JackTheBear]

It works for mining because the bandwidth requirements for mining are low. Mining can max out as much processing capacity as you have, but it doesn't need much bandwidth to do it. The mining program sends a task to each graphics card, the task being something like an equation. Each graphics card uses it's local resources (GDDR and cores) to solve the equation, then the graphics card(s) (hopefully) send back the answer, or the mining program tells them skip that equation, it's too late, here's a new equation. USB 2.0 is more than adequate for handling this traffic. It looks like that riser uses USB 3.0, probably for the increased speed of delivery, not for the total amount of data moved. Finding a block of Etherium means your computer solved the equation first. A 1 ms delay could cost you $4,500 so they used USB 3.0 even though it spends 90% of the day doing nothing just to reduce the latency and improve your odds.

For gaming, you need a lot of bandwidth for moving texture data, imagery, physics data, etc. back and forth to the CPU. If you want to game with this, you'll probably get 1/2 to 1/4 the performance you'd expect from the graphics card you install in it, and adding additional cards for SLI/CF would not improve anything.

 

[VirtualLarry]

It looks like that riser uses USB 3.0, probably for the increased speed of delivery, not for the total amount of data moved. Finding a block of Etherium means your computer solved the equation first. A 1 ms delay could cost you $4,500 so they used USB 3.0 even though it spends 90% of the day doing nothing just to reduce the latency and improve your odds.

No, the signalling is PCI-E, it's just that the physical cable is the same as USB3.0, due to construction, shielding, length, and support for differential signalling, as well as power and ground.

 

[Battousai01]

Thanks guys for the replies. So when it comes to mining, should I get a board that is designed for mining or should I just get any other board that has at least one PCI-E slot? The advantage if I get just any other board is that is is cheaper than a board designed for mining. What would you suggest?

 

[Lordhumungus]

Not a miner, so someone please correct me if I am wrong, but doesn't the motherboard itself require support for PCI-E bifurcation in order for these to work?

 

[PingSpike]

Not a miner, so someone please correct me if I am wrong, but doesn't the motherboard itself require support for PCI-E bifurcation in order for these to work?

No, I own one of these or at least a very similar one. It uses a switch/bridge chip. You can't see it in the picture, but its almost certainly a pericom bridge/switch. Bifrucation is something different I've gathered, basically a passive splitter that takes advantage of the bifrucation of the motherboard to do the work.

The pericom chips are pretty cheap and there's seemingly a flood of them on the market. I've seen them installed on low end combo SATA controller, USB3 controller devices. Basically some cheap off the shelf parts are put together to make a kind of unique combo product with the bridge chip.