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PCIe 4.0 support for selected X470 and B450 boards

ALB92
Level 8
Hello guys , i wanted to open this topic after reading this article from Guru3D : https://www.guru3d.com/news-story/ryzen-3000-asus-opens-up-pcie-4-support-for-selected-x470-and-b450... .

As stated in the article it apears that ASUS ( like other board manufacturers ) will offer PCIe 4.0 at least on X470/B450 wich is good but what is interesting here is that according to this list only low end boards like the Prime B450 Plus will get PCIe 4.0 x16 while high end boards such as Crosshair 7 Hero won't be able to run PCIe 4.0 at all ! Also both X470/B450 ITX boards won't be able to run PCIe 4.0 .

This makes absolutely no sense considering if low end mobos are able to run PCIe 4.0 then higher end ones should be able aswell especially in the ITX form factor wich should be warranted to work ! Does anyone here has more info to share on this or can someone from ASUS make a comment ?

Best regards .
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xeromist
Moderator
The more expensive boards are more complicated and none were designed for this. The simple boards don't have as much going on so they may be able to be tweaked more easily.

Also there may be a matter of validation. Due to the complexity of the high end boards ASUS may not feel comfortable enabling something that may cause unforeseen issues.

Practically speaking nobody needs this anyway. No GPU needs it and any SSD won't perform noticeably different. Perhaps in a year or two it will matter but by then these boards will be well outdated.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…

I just got a ROG STRIX B450-I and knew AMD has announced they were not going to support PCIe 4.0 on older motherboards, but if the chart is true and ASUS will enable PCIe 4.0 on the M.2_1 then that is all that matters to me since by the time there is a GPU that needs a PCIe 4.0 slot then PCIe 5.0 or 6.0 will be out and we will be on a new CPU socket/chip set.

xeromist wrote:
The more expensive boards are more complicated and none were designed for this. The simple boards don't have as much going on so they may be able to be tweaked more easily.

Also there may be a matter of validation. Due to the complexity of the high end boards ASUS may not feel comfortable enabling something that may cause unforeseen issues.

Practically speaking nobody needs this anyway. No GPU needs it and any SSD won't perform noticeably different. Perhaps in a year or two it will matter but by then these boards will be well outdated.


With all due respect this is total nonsense ! What complexity are you talking about ? It has nothing to do with being designed or not being designed for this , it happens that PCIe 4.0 requirements are not that much different from PCIe 3.0 it's just a matter of trace length and signal integrity . Most of X470/B450 ( or even X370/B350 for that matter ) boards should be able to run PCIe 4.0 on their first slot because that's the closest to the CPU , if anything else higher end boards have better built quality than lower end boards ( 6 layer PCB for something like Crosshair VII vs 4 layer PCB for TUF B450 ) so with this in mind considering low end ASUS boards are able to run PCIe 4.0 then higher end boards should have no issue whatsoever ! Same goes for ITX boards due to their size those should de facto meet the requirements .

I know that we don't really need PCIe 4.0 ( for now ) but that's another topic im not discussing about this here .

ALB92 wrote:
With all due respect this is total nonsense ! What complexity are you talking about ?


Just speculation, but given those boards are more complex/crowded I'm wondering if the traces are not as simple as the ones on the simpler boards. Also, even high quality traces could receive interference if there are other traces crowded nearby.

I could be wrong but there has to be a reason ASUS chose some boards as OK and some not.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…

xeromist wrote:
Just speculation, but given those boards are more complex/crowded I'm wondering if the traces are not as simple as the ones on the simpler boards. Also, even high quality traces could receive interference if there are other traces crowded nearby.

I could be wrong but there has to be a reason ASUS chose some boards as OK and some not.


More complex doesn't necessarily mean more crowded , you can have more features and still offer a better/ cleaner desing . For example both Crosshair 7 and TUF B450 feature similar layout , both have an m2 between CPU and first PCIe slot yet one offers PCIe 4.0 and the other doesn't wich makes no sense since as i alredy mentioned Crosshair 7 has a thicker PCB so there is much more space to properly run traces and properly shield them than on the TUF B450 , also higher end boards are specifically designed to offer better OC and stability wich means they have at least similar if not better trace layout/signal integrity than the lower end boards but certainly not worst ! Same goes for ITX those have much shorter trace length so even though they appear more ''crowded'' those should still offer better signal integrity due to shorter trace length than any ATX board .

To some this up there is no way that a 4 layer PCB boards ( read TUF B450 etc ) offers better signal integrity than a 6 layer PCB board ( read Crosshair etc ) with similar design unless the trace design on the 6 layer board is fondamentaly flawed !

For sure there has to be a reason but that might not be a good reason ! To me there can be only 2 logical explanations to this :

1) This is not a final list and ASUS is in the process of certifying the other boards .

2) This is a final list and in this case ASUS is artificialy crippling their high end X470/B450 boards because if those received PCIe 4.0 they would make most of their X570 boards redundant for most use case scenarios ! This or it would mean that their high end X470/B450 have been designed with much lower quality ( in terms of trace path etc ) than their lower end boards wich makes absolutely no sense !

Hence why i would like to hear a proper reason from an ASUS rep .

I'm wondering if it's smoke and mirrors, when I updated the BIOS on my B450-F it says Gen1,Gen2,Gen3 and Gen4 in the PCie 16 drop down. I ordered a 5700 XT and will try the GEN4 option when I get it. Also, ASUS did a BIOS update in May in advance of the 3000 series proccessors, if it doesn't work with the new update I'm going to flash back and see if the original update has it enabled, it came out well before AMD pulled the support. But then again I just got into this a few years ago, I'm just guessing.

shelleynme wrote:
I'm wondering if it's smoke and mirrors, when I updated the BIOS on my B450-F it says Gen1,Gen2,Gen3 and Gen4 in the PCie 16 drop down. I ordered a 5700 XT and will try the GEN4 option when I get it. Also, ASUS did a BIOS update in May in advance of the 3000 series proccessors, if it doesn't work with the new update I'm going to flash back and see if the original update has it enabled, it came out well before AMD pulled the support. But then again I just got into this a few years ago, I'm just guessing.


So your B450-F gives you a Gen 4 option with the latest BIOS if i understand you correctly ? If true that's a good thing because according to this list B450-F shouldn't get PCIe 4.0 so it would mean that this is only a preliminary list .
By the way you don't need a PCIe 4.0 GPU to test that you can enable PCIe 4.0 even when using a PCIe 3.0 GPU ( you won't see any difference between PCIe 4.0 and PCIe 3.0 anyways especialy not with something like a 5700XT but yeah thats another topic ) .

ALB92 wrote:
So your B450-F gives you a Gen 4 option with the latest BIOS if i understand you correctly ? If true that's a good thing because according to this list B450-F shouldn't get PCIe 4.0 so it would mean that this is only a preliminary list .
By the way you don't need a PCIe 4.0 GPU to test that you can enable PCIe 4.0 even when using a PCIe 3.0 GPU ( you won't see any difference between PCIe 4.0 and PCIe 3.0 anyways especialy not with something like a 5700XT but yeah thats another topic ) .


You understood correctly, got the card today, will test it out tonight and let you know. Bit of a noob though, after I switch it how will I know it's running in 4.0? Cheers.

So I selected GEN4 in the BIOS saved and reset. Seemed to be booting alright but then windows gave me an error message and restarted. Everything seemed ok and it booted to my desktop, I thought it was a success but then a loud sound started emanating from the speakers. I rebooted and got back to the desktop without any sound issues, I tried playing a Youtube video and the sound started off ok but then the voices got scratchy and the video actually paused. I rebooted again and got the same result. I switched back to auto in the BIOS, and everything is good again, so I guess unless they do another update GEN4 is a no go, for me at least.