AMD: Pre-X570 boards will not support PCIe Gen 4
Yes, that's what he said. Actually, AMD's Robert Hallock said that on Reddit. earlier on some motherboard manufacturers showed PCIe Gen 4.0 support in series 400 BIOSes.
And that confirms it plain and simple. The new 500 series chipset will support PCIe express Gen 4.0 in combination with Ryzern 3000 processors. Anything below, simply not. Whether or not you'll find PCIe 4.0 a buying feature is also topic of debate, your GPU certainly will not need that bandwidth, and while PCIe Gen 4.0 based NVMe SSD(s) are fun, would you truly really need 5000 MB/sec in SSD performance, other than for bragging rights of course .
"Hallock: This is an error we are correcting. Pre-X570 boards will not support PCIe Gen 4. There's no guarantee that older motherboards can reliably run the more stringent signaling requirements of Gen4, and we simply cannot have a mix of "yes, no, maybe" in the market for all the older motherboards. The potential for confusion is too high. When final BIOSes are released for 3rd Gen Ryzen (AGESA 1000+), Gen4 will not be an option anymore. We wish we could've enabled this backwards, but the risk is too great."
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PCIe Version | Line Code | Transfer Rate | x1 Bandwidth | x4 | x8 | x16 |
1.0 | 8b/10b | 2.5 GT/s | 250 MB/s | 1 GB/s | 2 GB/s | 4 GB/s |
2.0 | 8b/10b | 5 GT/s | 500 MB/s | 2 GB/s | 4 GB/s | 8 GB/s |
3.0 | 128b/130b | 8 GT/s | 984.6 MB/s | 3.938 GB/s | 7.877 GB/s | 15.754 GB/s |
4.0 | 128b/130b | 16 GT/s | 1.969 GB/s | 7.877 GB/s | 15.754 GB/s | 31.508 GB/s |
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Would have made x570 useless i believe. What does it do other than giving you pci express 4?
I belive someone will tweak the bios to try it out
The chipset being connected through PCIe 4.0 is a much bigger deal then getting PCIe4 to the GPU, because it doubles the bandwidth the chipset has available. And this of course only works if the chipset is PCIe4 capable, so only X570.
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We don't know Matisse performance difference between X470 and X570. Hopefully it's minimal.
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at least i think there might be attempts for it

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PCIe 4.0 has much more stringent requirements, though. On a board with multiple x16 slots, you'll already need re-drivers to enhance the signal to reach the bottom slots at full signaling strength.
Any test with PCIe 3.0 doesn't prove anything, since these things often interact exponentially. Also note that signaling in motherboard traces and in shielded cables of an extender is actually quite different, and shielded cables can go further without as much loss - but thats not an option for putting inside the PCB.
I would like to see extension cards/cords for PCIe 4.0. This may hinder system builders a lot then. And something that sensitive does not sound right either.
Things called standard are supposed to work. Does that means that dream of external PCIe 4.0/5.0 devices is gone?
Seems really weird to go from 10 interconnected PCIe 3.0 extensions 6 meters long working connection down to problems directly connecting on MB itself on few centimeters distance.
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I don't see why they couldn't leave the option enabled for older mobos, turned off by default, of course.
Having an option that doesn't work is a support nightmare, and the points about confusion cited as the reason still stand.