Well, you could say I should have known better - yet, I tried:
Recently, I saw an article about the new RealTek RTL8127 NIC. On paper, it looks fine: 10/5/2.5/1 Gbps, low power draw and PCIe 4.0 x1 interface, which makes it easy to fit into any mainboard - or so it seems.
Main main reason to use it were the shortcomings of other high speed RJ45 adapters, like the X550-T1. That one:
- uses much more power
- needs a PCIe 3.0 x4 slot
- cannot handle autonegotiation on some OSes
Because I have not-so-good CAT.5E cabling, I like to use 5 Gbps, but with newer Windows drivers, you cannot even fix speeds at NBase-T (5 or 2.5 Gobs), so you are mostly stuck with 1 or 10 Gbps only. Linux is a prominent example where the driver allows intermediate speeds, see this for details (https://forum.opnsense.org/index.php?topic=48933.0).
I already had a Realtek RTL8126, which can do 5 Gbps at most, but that one had a quirk: On cold boots, it was sometimes not detected at all. Only a power-cycle would help. The internet is full of discussions about that. So, I went for it and bought the RTL8127...
...only to find that it had the same quirk.
But now comes the hard part: My Windows 11 installation has gone awry in the last few weeks. Basically, I could not start Steam and Ollama any more. Nothing I did could repair it.
On I went with a new installation from scratch and restoration of my user files afterwards. Then, I had to install every application again.
System worked fine for ~24 hours, then I noticed strange things happening: My desktop icons flashed ever 0.5 seconds and I could no longer set the default browser. No repairs worked here, either.
Since I still had the profile backup, I decided to repeat the whole process. While I was doing that, I tried to relocate the RTL8127 into another PCIe slot. This time, the restoration of my user profile showed 3 CRC errors. I was quite sure there were no problems on the source.
So, the plot thickened: Obviously, in my X570 board, the PCIe 4.0 slots attached to the chipset have problems. The X570 chipset was the first to use PCIe 4.0, so the implementation may be flaky. At the time, nobody would have noticed, because most PCIe cards only supported PCIe 3.0 anyway.
Now, the problem manifests in two ways:
1. The NICs may sometimes go undetected during cold start PCIe training.
2. The data that is transferred to the mainboard can get corrupted. This became very obvious when I installed some 500 GByte of software and data over the network.
I am quite sure that this caused all the other problems, too.
TL;DR: The newer Realtek chips RTL8126 and RTL8127 do not run reliably on older hardware that "supports" PCIe 4.0.
Of course, this is independent of OS. You might also say that is not Realtek's fault, but at least, it does not happen with the Intel X550-T1, which only uses PCIe 3.0. BTW: It only works with either PCIe x4 or x1, so my x2 slot was a waste.
I'd punish you by sending you all of my old Aquantia and Tehuti hardware, but the joke wouldn't be worth the ridiculous international shipping.
It might not be worth it, but you should be able to set the PCI-e version in the BIOS. (I can find it easily, but only if I'm looking at it.)
Nope. In that BIOS, I can only set the PCIe speed for the CPU lanes and the chipset lanes separately, not per slot. And since the CPU lanes are solely used for the graphics card, I can only set all of the chipset lanes together, crippling my NVME drives.
Apart from that, I suspect that these problems are with the NICs - when you skim through the reports, you will find newer affected chipsets like X870. I doubt that my Asrock board is the culprit here and maybe even going back to PCIe 3.0 would not cut it.
After having seen these corruption problems and all my time invested chasing ghosts, I won't place any more bets on these things, either.
P.S.: I have an Aquantia here, as well. Never worked right. I even had a conversation with their CEO on that back in the day...
Quote from: meyergru on February 11, 2026, 10:10:11 PMIn my X570 board, the PCIe 4.0 slots attached to the chipset have problems.
The X570 chipset was the first to use PCIe 4.0, so the implementation may be flaky.
At the time, nobody would have noticed, because most PCIe cards only supported PCIe 3.0 anyway.
IIRC there were plenty of websites that wrote a lot about that issue when the AMD Chipset was released ?!
IMHO a great part of the issues comes from the fact that ASMedia a.k.a. ASUS was involved in the design and manufacturing process of the Chipset at the time.
Do you have any Intel based systems to test with ?
I am pretty much done with buying AMD for about 15 years or so now...
No, but the reports on the internet were all over the place and some were Intel boards, too, like this:
https://www.reddit.com/r/Fedora/comments/1p1syhw/realtek_rtl8127_dropping_out/