ASUS reveals PCIe 4.0 support for much of their X470 range of motherboards

Some models boast PCIe 4.0 connectivity, others are stuck with 3.0.



Read more about ASUS' 400-series AM4 motherboards supporting limited PCIe 4.0 support.

i read that correct? the cheaper boards support PCI 4.0 on the fist PCI slot while the expensive ones do not?

Doesn't this kind of contradict everything we have been told previously on how PCI-e 4 needed additional hardware that was not in use for PCI-e 3 and that the chipsets would need cooling to manage the additional load on the chipset?
And that this was the justification for the additional price (extra layers needed in the PCB to support the additional connections and more expensive chipset)?
I mean a crosshair 7 is around the 270 to 300 price where as a crosshair 8 is 400.
Something is not right here, admittedly a bonus for anyone on the x470 but if you have bought a x570 because everyone involved told you that you had to if you wanted PCI-e 4 (AMD, board manufacturers, reviewers ect) is kind of misleading and possibly liable.
https://www.anandtech.com/show/14477/amd-confirms-pcie-4-not-coming-to-older-motherboards

demonking said:

Doesn't this kind of contradict everything we have been told previously on how PCI-e 4 needed additional hardware that was not in use for PCI-e 3 and that the chipsets would need cooling to manage the additional load on the chipset?
And that this was the justification for the additional price (extra layers needed in the PCB to support the additional connections and more expensive chipset)?
I mean a crosshair 7 is around the 270 to 300 price where as a crosshair 8 is 400.
Something is not right here, admittedly a bonus for anyone on the x470 but if you have bought a x570 because everyone involved told you that you had to if you wanted PCI-e 4 (AMD, board manufacturers, reviewers ect) is kind of misleading and possibly liable.
https://www.anandtech.com/show/14477/amd-confirms-pcie-4-not-coming-to-older-motherboards

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The prominent issue is signal integrity. You can see that m.2 slots are just below the CPU. They are very close and, as stated in the article, those are primary m.2 slots with CPU lanes. Also with PCIe x16 slot, only boards that don't support SLI/CF have some support for PCIe 4.0. Again, they have only one PCIe slot that is connected to CPU. Boards that have lane dividers (a bunch of those square chips that you see between PCIe slots) and support for SLI/CF, in this case, higher-end boards, don't support PCIe 4.0. The second slot is very far from the CPU, and lane dividers don't support PCIe 4.0. That why you need better-built PCBs, and different components. ITX boards have extremely densely packed PCBs, with traces going all around everywhere so I assume it is too noisy to keep adequate signal integrity for PCIe 4.0, hence no support.

PCH has nothing to do with support on x470 boards because support is related only to CPU lanes.

If you know very basic stuff about PCIe lanes, and how stuff is organized on the motherboard it is very logical and makes sense.

If there are any engineers there please correct me if I am wrong.

Avet said:

The prominent issue is signal integrity. You can see that m.2 slots are just below the CPU. They are very close and, as stated in the article, those are primary m.2 slots with CPU lanes. Also with PCIe x16 slot, only boards that don't support SLI/CF have some support for PCIe 4.0. Again, they have only one PCIe slot that is connected to CPU. Boards that have lane dividers (a bunch of those square chips that you see between PCIe slots) and support for SLI/CF, in this case, higher-end boards, don't support PCIe 4.0. The second slot is very far from the CPU, and lane dividers don't support PCIe 4.0. That why you need better-built PCBs, and different components. ITX boards have extremely densely packed PCBs, with traces going all around everywhere so I assume it is too noisy to keep adequate signal integrity for PCIe 4.0, hence no support.

PCH has nothing to do with support on x470 boards because support is related only to CPU lanes.

If you know very basic stuff about PCIe lanes, and how stuff is organized on the motherboard it is very logical and makes sense.

If there are any engineers there please correct me if I am wrong.

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Hey, Not doubting this is possible the article even mentions that there should be no reason why those that have over engineered their PCI-e interface cannot.
Doubting as to why a Robert Hallcock of AMD tells the world if you want PCI-e 4 on any of its chips you have to buy an x570 and then Asus come out and say this was not true.

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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Watch TTL's own review on the Ryzen 3 chips where he talks about how x570 is going to be more expensive and how this is justified. or GN or J2C or any other review

intel will push to PCI 5.0 just to give amd the finger.


for me PCI 4.0 is no buying argument at all.


i rather buy a x470 for 250 euro then a x570 for 440 euro.
crappy chipset fans, new chipset with possible issues etc...

when i NEED PCI 4.0 in the future i will probably buy another mainboard anyway.... or PCI 5.0 will be the new standard.

X570 is more expensive because of the chip itself, its the first time a Ryzen chipset has been designed by AMD and its the first time one has used 12nm GloFlo, the cost will be down to the more modern node and larger than typical die size for a chipset. The increased costs from the extra PCB layers or cooling will be essentially negligible here.

What Robert says is correct, here the boards themselves are not supporting a PCIe4 interface, they're using the small amount of lanes exposed directly from the chipset die within the CPU package itself(All Ryzen processors are full SoCs with some chipset functionality built in the package). They'd clearly rather manufacturers didn't do this as it creates boards which vary across slots and stuff but can't control them at the end of the day.

Sweet my ITX board supports m.2 4.0

I've wanted a faster a NVMe drive... Now if we can just get reviews on them that are actually in depth

There is a difference between AMD supporting a feature, and motherboard manufacturers forcing it to work. As said above it's all about signal integrity, something that's only reliably achieved on X570.

X570 boards are overbuilt, they need to be to guarantee stability in the long haul and to allow PCIe 4.0 to work on PCIe lanes that are far from the CPU and are connected to the chipset or other I/O sections of a motherboard. X570 offers PCIe 4.0 all over the place, whereas 400-series boards can only offer it in some circumstances on only the top PCIe 16x lane (even then rarely), and on the primary M.2 slot that connects directly to the CPU.

Don't expect PCIe 4.0 to work on M.2 slot 2, or on strange configurations where PCIe lanes were split or had some other strangeness going on. MSI's Godlike motherboards etc come to mind.

The lack of consistency is what forced AMD to not officially support PCIe 4.0 on 400 series motherboards. Beyond that, most 400-series boards on the market today probably lack drop in support for Ryzen 3rd Gen, which adds even more problems into the mix for new buyers.

I don't know why people are complaining. AMD gave you an option when first Ryzen launched to use any board with any CPU. Please don't put 12 core CPU on the cheapest B350 motherboard. AM4 will be supported until 2020, so at least one more CPU release. Choose your board and be happy with it, and stop complaining.

Ryzen 3000, as have all Ryzen releases before it, is months too early. Again with AGESA updates every few days. Bugs left, right and center. Playback in Premiere not working, Destiny 2 not working. CPUs not hitting advertised clocks. It is not possible that AMD devs didn't know about this stuff. Even Wendell from Level1techs has no clue what is happening and that tells you a lot. It is a good product, but it is a mess at the moment.

The reason things are going down like this is literally down to how the board etc is built. It's luck mostly. However, AMD could not guarantee PCIE 4.0 would work on every existing board.

It's kinda like that time you could patch your PCIE 2.0 rig to 3.0 if you had at least an Ivy CPU. In fact, you could even enable PCIE 3.0 on certain Sandy CPUs (3970x was one).

Still there's no need to complain if you buy a 400 series board. They are still the same price they were before 570x came out. And, probably the better to live with too.

AlienALX said:

The reason things are going down like this is literally down to how the board etc is built. It's luck mostly. However, AMD could not guarantee PCIE 4.0 would work on every existing board.

It's kinda like that time you could patch your PCIE 2.0 rig to 3.0 if you had at least an Ivy CPU. In fact, you could even enable PCIE 3.0 on certain Sandy CPUs (3970x was one).

Still there's no need to complain if you buy a 400 series board. They are still the same price they were before 570x came out. And, probably the better to live with too.

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Back in the x79 days, if you had the right board, you had PCIE 3.0 on every socket 2011 CPU. I had it on my 3820k. But you needed a high end board (mine was the Asus Rampage IV Gene). That board was advertised as "PCIE 3.0 ready" at the time.

Avet said:

I don't know why people are complaining. AMD gave you an option when first Ryzen launched to use any board with any CPU. Please don't put 12 core CPU on the cheapest B350 motherboard.

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i don´t see complains here regarding that.


personally i just wonder that the cheap TUF boards get support for PCI 4.0 on the first PCIE slot and the way more expensive crosshair not....

Gothmoth said:

i don´t see complains here regarding that.


personally i just wonder that the cheap TUF boards get support for PCI 4.0 on the first PCIE slot and the way more expensive crosshair not....

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signal integrity...

NeverBackDown said:

signal integrity...

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still suprising that signal integrity is better on cheaper boards. not?


you could think a bit of the money goes into better PCB and signal integrity for OC boards like the cosshair. not just water pump connections, fan headers, rgb lighting and stuff.

Bartacus said:

Back in the x79 days, if you had the right board, you had PCIE 3.0 on every socket 2011 CPU. I had it on my 3820k. But you needed a high end board (mine was the Asus Rampage IV Gene). That board was advertised as "PCIE 3.0 ready" at the time.

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MSI Big Bang Xpower 2 (try saying that with a mouthful of cornflakes !). Also worked on my RIVE when the BB took a big bang and blew up

Hehe I almost called it right on the day of the release, I queried if AMD / Asus had cooked up some magic to allow PCIE to run from the CPU. Now all I need is for Samsung to release some NVMe hitting 6GB/s

Cleaned up the thread a bit. No need for name calling or trying to bypass the swear filters.

Gothmoth said:

still suprising that signal integrity is better on cheaper boards. not?


you could think a bit of the money goes into better PCB and signal integrity for OC boards like the cosshair. not just water pump connections, fan headers, rgb lighting and stuff.

Click to expand...

I have already explained it in the previous post.

Avet said:

The prominent issue is signal integrity. You can see that m.2 slots are just below the CPU. They are very close and, as stated in the article, those are primary m.2 slots with CPU lanes. Also with PCIe x16 slot, only boards that don't support SLI/CF have some support for PCIe 4.0. Again, they have only one PCIe slot that is connected to CPU. Boards that have lane dividers (a bunch of those square chips that you see between PCIe slots) and support for SLI/CF, in this case, higher-end boards, don't support PCIe 4.0. The second slot is very far from the CPU, and lane dividers don't support PCIe 4.0. That is why you need better-built PCBs and different components. ITX boards have extremely densely packed PCBs, with traces going all around everywhere so I assume it is too noisy to keep adequate signal integrity for PCIe 4.0, hence no support.

PCH has nothing to do with support on x470 boards because support is related only to CPU lanes.

If you know very basic stuff about PCIe lanes, and how stuff is organized on the motherboard it is very logical and makes sense.

If there are any engineers there please correct me if I am wrong.

Click to expand...

Just to clarify a couple of points regarding signal integrity as i think this is where the discussion is breaking down

Because PCIe is a serial bus there is a lot of very high frequency switching going on
High frequency signals can create issues regarding leaking (cross coupling) into nearby traces
What is ok for one switching frequency may not be ok for another
If a board was tested to work acceptably with PCIe3.0 there is no guarantee that it will work well for PCIe4.0
The distance between traces, the angle at which traces cross other traces, how many layer changes the traces go through the proximity to certain components all affect a trace's ability to carry a signal and what frequency those signals can be.

The ability to do good circuit board layout is almost black magic as it is. Sometimes the person doing the layout doesn't even know what the individual traces are doing. They are just given a list of rules that must be followed.

So while it may seem arbitrary what boards do and don't support PCIe4.0 it's most likely down to some design decisions were made that were completely fine, or possibly better, for PCIe3.0 that are not fine for PCIe4.0.

These decisions are not as clear cut as lower quality parts or cheaper copper, but highly nuanced.