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PCIE v4 and riser cables

Soldato
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A number of cases like the Dan A4 depend upon riser cables to connect the motherboard to the GPU. Will these cables still give full bandwidth with PCIE v4? Will new cables be necessary? Or will cables not be possible?
 
Associate
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good question. I was wondering this myself. I just hope Asus will allow PCIE 4.0 with a bios update on my B450-I, Its perfect size for my build. These new Cooling systems on the new Mobos are insanely big and will make me have to rethink where my pump is.
 
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A number of cases like the Dan A4 depend upon riser cables to connect the motherboard to the GPU. Will these cables still give full bandwidth with PCIE v4? Will new cables be necessary? Or will cables not be possible?
Educated guess but a cable is just wiring. As long as they don't fiddle with the connections, which they wont for backwards compatability, cable should not matter. Are riser cables rated as pcie 3 currently?
 
Soldato
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Educated guess but a cable is just wiring. As long as they don't fiddle with the connections, which they wont for backwards compatability, cable should not matter. Are riser cables rated as pcie 3 currently?

Yes, and I remember there being issues with those to start with.
 

HeX

HeX

Soldato
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Educated guess but a cable is just wiring. As long as they don't fiddle with the connections, which they wont for backwards compatability, cable should not matter. Are riser cables rated as pcie 3 currently?

I'm sure I've read that PCI-E 4.0 bandwidth is dependant on the distance the signal has to travel, if you start adding in extensions then you might be fine for PCI-E 3.0 but possibly not for 4.0...
 
Soldato
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Given all the talk about signal integrity and interference issues that had to be tackled to make PCIe 4.0 work on x570 I doubt that a PCIe riser cable would support it. However if you are using the PCIe slot for a GPU then the extra bandwidth of 4.0 won't benefit you anyway.
 
Soldato
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Cables are likely not as problematic as PCB traces, but there are additional connections too. As a pure guess I think you'd be looking at new more expensive riser cables with higher quality and/or retimers built in to maintain the 4.0 speeds.... debatable whether it matters given the bandwidth requirements of current GPUs though. I'm sure someone will do some tests with PCIe 4.0 boards and riser cables to see if there is any frame rate impact.


edit - interesting quote

“What we have been using for 4.0 and expect to use for 5.0 is twinax cables and firefly connectors,” he added. “The cost is very low compared to retimers, you can get whatever you want in distance, and the latency is really good.”

Indeed, Krause noted that “there’s been a lot of interest in using cables … for every inch on a board, you can go 10 inches on cables for the same power and loss budget, but cables have costs in being routed and connected.”

https://www.eetasia.com/news/article/18061502-pcie-45-higher-bandwidth-but-at-what-cost
 
Soldato
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A number of cases like the Dan A4 depend upon riser cables to connect the motherboard to the GPU. Will these cables still give full bandwidth with PCIE v4? Will new cables be necessary? Or will cables not be possible?

if you have the dan 4 then that will ship with gen 3 riser cable, my dan a4 v4.1 shipped with a gen 4 riser cable, also nzxt's new h1 case comes with a gen 3 but has plans to offer a upgrade to owners of the first run cases, it was said to be working on a new revision of the h1 that includes a gen 4 riser standard.
when they were designing the case gen 4 wasn't a thing until it came to market, so instead of delaying the case launch they decided to ship with gen 3 risers instead.

tbh gen 4 pci-e is in its infancy and no real world use cases so any real benefit to using it, gen 3 will work perfectly fine as is :)
 
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