Realtek 10 GbE USB Adapters might be on the way?

[SlowmoDK]

I have been holding out on buying the RTL8159-based Diewu/XikeStor/Lekuo USB adapters because they're still quite bulky.

My hope was for something as small and light as Ubiquiti's 5GbE USB adapters to show up at some point. That one is only 38g!

The Diewu is 66g and feels like a quality assembly.

Right now I have a hard time imagining a sub 50gram device without sacrificing build quality or thermals

But hopefully time proves me wrong

 

[Bulls729]

…But I have been wondering if it's reasonable to expect something that small….

iOCrest makes a USB4 10GbE Adapter that is 4x1.6x1in so not too much bigger, but not based on the RTL chipset.

 

[Bulls729]

Cable Matters has an RTL8159-based adapter up on Amazon now: Cable Matters USB C to 10Gb Ethernet Adapter

Nice to see a recognizable brand getting product to market on the 8159, but their marketing on this listing is pretty bad and honestly it's going to cause confusion for a lot of the less technical buyers who find it.

The product title leads with "Compatible with USB4 & Thunderbolt 5/4/3" like that's the headline feature, and then they quote "real-world speed" of ~7Gbps on Windows and ~5Gbps on macOS. On the Mac side they even acknowledge the OS only reports a 5Gbps link rate. They're framing those numbers like it's just normal 10GbE overhead, when what's actually happening is the adapter is bandwidth-starved because TB and USB4 ports are not the primary interface for the 8159.

The RTL8159 is USB 3.2 Gen 2x2. It needs a 2x2 host, two bonded 10Gbps superspeed lanes for 20Gbps of USB bandwidth, to actually deliver 10GbE. That ~7Gbps figure is what happens when you plug it into a port that only hands it a single Gen 2 lane, which is exactly what a USB4 or Thunderbolt port does when it sees a USB 3.x device.

For anyone following the RTL8159 and wondering why a "20Gbps USB adapter" doesn't work at full speed on a "40Gbps Thunderbolt port." The USB-IF created one of the worst branding situations in consumer tech history here, and products like this are the direct result.

USB development essentially forked into two completely different paths. Gen 2x2 was the last evolution of traditional USB 3.x take Gen 2 signaling at 10Gbps and bond two lanes together for 20Gbps. Same underlying USB superspeed protocol, just doubled up. It needed its own host and device controllers specifically designed for that lane-bonding approach.

USB4 went in a different direction. Intel donated the Thunderbolt 3 protocol to the USB-IF as a royalty-free specification, and that became USB4. So USB4 is fundamentally Thunderbolt, it tunnels multiple protocols (PCIe, DisplayPort, USB 3.x) over a shared link using what is essentially a PCIe-based fabric. That's why USB4 is backwards compatible with TB3/TB4/TB5, they're all speaking the same language at the physical layer.

So you ended up with two technologies that both use USB-C, both offer 20Gbps+, and both have "USB" in the name, but they are architecturally different. Gen 2x2 bonds traditional USB superspeed lanes. USB4/Thunderbolt tunnels protocols over a PCIe fabric. Different controllers & signaling that are not interchangeable in the way the shared branding implies. A USB4/TB controller doesn't have the lane-bonding hardware that 2x2 requires, and a 2x2 controller doesn't use the tunneling protocol that USB4/TB uses. When a Thunderbolt or USB4 port encounters a USB 3.x device like the RTL8159, it just falls back to standard USB 3.x compatibility, single Gen 2 lane, 10Gbps, done.

This is why the Aquantia/Marvell-based adapters (AQC113 etc.) deliver 10GbE over Thunderbolt and USB4. They aren't USB 3.x devices, they tunnel PCIe over the TB/USB4 link, using the native protocol of those ports.

None of this is a knock on the RTL8159 itself. For anyone with a proper Gen 2x2 port, mostly certain desktop boards with the right host controller, this is going to be a killer value for 10GbE over USB. But Gen 2x2 ports aren't common, especially on laptops, and that's the disconnect with Cable Matters marketing this thing at the Thunderbolt/USB4 crowd.

I left a review on the Amazon listing trying to explain all of this for regular buyers, but figured it was worth flagging here too since I know people in this thread are following the 8159 rollout. If Cable Matters' product team is paying any attention, they really need to rework that listing. Lead with the Gen 2x2 requirement, put TB/USB4 in the fine print where it belongs. The USB-IF already made this confusing enough without vendors making it worse.

 

[Shonk]

" Nice to see a recognizable brand getting product to market on the 8159 "

Its not really a recognizable brand they simply buy in from china direct and have customized branding
in alot of cases you are far better getting it direct

this is a perfect example they have ordered a customized version
then when they have arrived the person charged with doing the marketing material for cable matters
has no idea of the specs and such to market it so messed the whole thing up

 

[SlowmoDK]

I left a review on the Amazon listing trying to explain all of this for regular buyers, but figured it was worth flagging here too since I know people in this thread are watching the 8159 rollout. If Cable Matters' product team is paying any attention, they really need to rework that listing. Lead with the Gen 2x2 requirement, put TB/USB4 in the fine print where it belongs. The USB-IF already made this confusing enough without vendors making it worse.

There is nothing wrong with that listing, very sober and explains use cases.
Not a single wrong claim is made, even states expected speed using USB4/Thunderbolt, and for best performance use usb3.2

 

[Shonk]

There is nothing wrong with that listing, very sober and explains use cases.
Not a single wrong claim is made, even states expected speed using USB4/Thunderbolt, and for best performance use usb3.2

Thats why you should not work in marketing
your another one who doesnt know what he is talking about
everything Bulls729 said is correct

 

[SlowmoDK]

Thats why you should not work in marketing

Please point me to a single fault in the listing

 

[Shonk]

Please point me to a single fault in the listing

Its not my job to teach you how to drink milk
dont run your mouth about things you have a surface level understanding of

 

[Bulls729]

" Nice to see a recognizable brand getting product to market on the 8159 "

Its not really a recognizable brand they simply buy in from china direct and have customized branding
in alot of cases you are far better getting it direct

this is a perfect example they have ordered a customized version
then when they have arrived the person charged with doing the marketing material for cable matters
has no idea of the specs and such to market it so messed the whole thing up

Yes, they're sourcing from the same Chinese ODMs as everyone else, and yes in a lot of cases you can find the same underlying product for less if you go direct or grab a white-label version. That's true of most of the accessory brands in this space. But Cable Matters has built a presence over the years, they show up in buying guides, they get recommended on forums like this one and on Reddit, and they have a track record with reviewers. For a less technical buyer shopping on Amazon, seeing "Cable Matters" on a listing carries more weight than seeing a random string of letters with zero review history. They occupy the same tier as Monoprice, UGREEN, Anker, where the average consumer sees the name and assumes a level of vetting and quality above the no-name stuff. Whether this was a deliberate framing choice or just someone on their marketing team not fully grasping the distinction between Gen 2x2 and USB4/Thunderbolt, the end result for the buyer is the same.

EDIT: To clarify further, when these newer Realtek chips first hit the market, whether it's the RTL8127, 8159, or whatever comes next, the purchasing path is always the same. You're hunting down listings on Aliexpress, Alibaba, eBay, hoping the seller is legit, waiting on shipping from Shenzhen, and sometimes buying in bulk just to get a reasonable per-unit price. Eventually IOCrest picks them up, then the broader brands follow. Cable Matters getting an RTL8159 product onto Amazon matters for the people who aren't going to navigate that import pipeline.

There is nothing wrong with that listing, very sober and explains use cases.
Not a single wrong claim is made, even states expected speed using USB4/Thunderbolt, and for best performance use usb3.2

Your'e correct, nothing on the listing is a false claim. My point is about framing and emphasis.

When the product title leads with "Compatible with USB4 & Thunderbolt 5/4/3" and the ~7Gbps/~5Gbps figures are buried as "real-world speed" disclaimers, it presents an architectural bottleneck as if it's just normal benchmark-to-reality variance. Those aren't in the same category. One is expected overhead, the other is the port physically not having enough bandwidth for the chipset. The distinction matters to a buyer deciding whether this is the right adapter for their setup.

I get that from a support perspective, it makes sense to set expectations for the ports most buyers actually have. Most people shopping for a random USB NIC probably do have USB4 or TB and not a Gen 2x2 port, and I can see the logic in getting ahead of that. But the listing could accomplish the same thing by leading with the 2x2 requirement and noting TB/USB4 performance as secondary, rather than the other way around. Right now the hierarchy is inverted.

Anyone buying 10GbE should know what they're getting into. But this is Amazon, and the reality is most buyers don't cross-reference datasheets before clicking buy. It's the same thing that happens with "Cat7 and Cat8" cable listings. People see "Cat8 40Gbps Gaming Cable" for $15 and grab it for their 1Gbps router when their existing Cat5e patch cable running 10 feet would perform identically. But bigger numbers sell. Same dynamic here.

 

[Shonk]

Yes, they're sourcing from the same Chinese ODMs as everyone else, and yes in a lot of cases you can find the same underlying product for less if you go direct or grab a white-label version. That's true of most of the accessory brands in this space. But Cable Matters has built a presence over the years, they show up in buying guides, they get recommended on forums like this one and on Reddit, and they have a track record with reviewers. For a less technical buyer shopping on Amazon, seeing "Cable Matters" on a listing carries more weight than seeing a random string of letters with zero review history. They occupy the same tier as Monoprice, UGREEN, Anker, where the average consumer sees the name and assumes a level of vetting and quality above the no-name stuff. Whether this was a deliberate framing choice or just someone on their marketing team not fully grasping the distinction between Gen 2x2 and USB4/Thunderbolt, the end result for the buyer is the same.



Your'e correct, nothing on the listing is a false claim. My point is about framing and emphasis.

When the product title leads with "Compatible with USB4 & Thunderbolt 5/4/3" and the ~7Gbps/~5Gbps figures are buried as "real-world speed" disclaimers, it presents an architectural bottleneck as if it's just normal benchmark-to-reality variance. Those aren't in the same category. One is expected overhead, the other is the port physically not having enough bandwidth for the chipset. The distinction matters to a buyer deciding whether this is the right adapter for their setup.

I get that from a support perspective, it makes sense to set expectations for the ports most buyers actually have. Most people shopping for a random USB NIC probably do have USB4 or TB and not a Gen 2x2 port, and I can see the logic in getting ahead of that. But the listing could accomplish the same thing by leading with the 2x2 requirement and noting TB/USB4 performance as secondary, rather than the other way around. Right now the hierarchy is inverted.

Anyone buying 10GbE should know what they're getting into. But this is Amazon, and the reality is most buyers don't cross-reference datasheets before clicking buy. It's the same thing that happens with "Cat7 and Cat8" cable listings. People see "Cat8 40Gbps Gaming Cable" for $15 and grab it for their 1Gbps router when their existing Cat5e patch cable running 10 feet would perform identically. But bigger numbers sell. Same dynamic here.

That was a well thought out and explained reply
i couldnt be bothered doing it as they generally double down no matter what you say

 

[Bulls729]

Timely example of exactly what I was talking about. Jake (Jakkuh, formerly of LTT) just posted his MacBook Neo review and at around 17:31 he tests an RTL8159-based adapter. The Neo doesn’t have USB 3.2 Gen 2x2, it tops out at a single Gen 2 lane (10Gbps) on the rear USB-C port. So the adapter is already bandwidth-limited before you even get to the macOS side of things which the macOS driver stack doesn’t currently recognize these RTL8159 adapters as 10GbE controllers, so the OS itself is capping the link rate at 5GbE.

Jake seemed genuinely confused about what was happening, and he’s not someone you’d call technically illiterate. But the marketing on these adapters is poor. He hit the exact wall that we’ve been discussing in this thread, bought/received a “10GbE USB-C adapter,” plugged it into a USB-C port, and didn’t get 10GbE.

This is exactly the kind of person who would read the listing, see “Compatible with USB4 & Thunderbolt” or even just “USB-C 10GbE,” and have no reason to think twice about plugging it into a Mac with a USB-C port.

 

[WhiteNoise]

You are correct. Unfortunately not all USB4 (and thunderbolt) can do USB 3.2 2x2, actually most don't. USB4 only mandates USB 3.2 Gen 2x1.

As I said in another thread, USB 3.2 2x2 is actually pretty rare, it would have been better if Realtek made this a USB4 native device.

I put most of the blame of this mess on USB

 

[Bulls729]

You are correct. Unfortunately not all USB4 (and thunderbolt) can do USB 3.2 2x2, actually most don't. USB4 only mandates USB 3.2 Gen 2x1.

As I said in another thread, USB 3.2 2x2 is actually pretty rare, it would have been better if Realtek made this a USB4 native device.

I put most of the blame of this mess on USB

Trust me, I went in depth about this in post #209

 

[Shonk]

Gen 2 x 2 was always an optional part of the USB 4.0 i dont actually know of any chipset (e.g. PCH) that implemented it
Intel didnt the only company that may have is asmedia on an addon controller

 

[Shonk]

AsMedia ASM4242 thats it

 

[Patriot]

Please point me to a single fault in the listing

When the likely issue is 3.2 gen2x1
It was explained in a previous post already, they are implying that the lower performance is a windows overhead thing, not a USB branding/confusing thing of USB4 not always supporting gen3.2x2 performance due to the change in architecture to thunderbolt.
The marketing material is happy to let customers have poor performance.

If you demand information, while ignoring what has already been said, you might frustrate your sources of information.

Its not my job to teach you how to drink milk
dont run your mouth about things you have a surface level understanding of

I know you may feel strongly about those that are poor receptors of information... but tone down the harshness...

 

[SlowmoDK]

Gen 2 x 2 was always an optional part of the USB 4.0 i dont actually know of any chipset (e.g. PCH) that implemented it
Intel didnt the only company that may have is asmedia on an addon controller

Not true

I have tested my RTL8159 on three different USB4/Thunderbolt ports, all 3 gave me the full 20Gbps aka 2 10Gbps lanes
2 ports based on Intel and one from AMD

So the marketing is actually not that misleading at all..

Does USB4 ports exists that doesn't support gen3x2 proberly yes, but it far from all that dosen't

 

[Patriot]

Not true

I have tested my RTL8159 on three different USB4/Thunderbolt ports, all 3 gave me the full 20Gbps aka 2 10Gbps lanes
2 ports based on Intel and one from AMD

So the marketing is actually not that misleading at all..

Does USB4 ports exists that doesn't support gen3x2 proberly yes, but it far from all that dosen't

No, it is not a mandated part of USB4 spec.
Yes the marketing is implying bad performance is a driver issue and not a port issue.

7Gbps or worse is due to 1 lane tunneling, not a driver, that is bad information and outright misleading.
I am not sure why you are choosing this hill to die on, did you write this marketing material?

Devices with USB4 that do have the higher speed ports often have other ports that are only 10 or 20Gbps... connecting to those would cause issues that might be unexpected if the marketing only says gen3.2x2 for best performance and a port labeled USB4 20Gbps can still be 1 lane... and not give the required performance.

 

[WhiteNoise]

In my anecdotal experience with thunderbolt 3 and 4 controllers, most of them didn't do USB 3.2 Gen 2x2. Also USB4 is based on Thunderbolt3 but is not Thunderbolt3.

I think the marketing copy of Cable Matters is not horrible and this mess is not their fault. The say typical 7 Gbps windows because I am sure they terrified by the returns.

 

[SlowmoDK]

No, it is not a mandated part of USB4 spec.
Yes the marketing is implying bad performance is a driver issue and not a port issue.

7Gbps is due to 1 lane tunneling, not a driver, that is bad information and I am really boggled why you are standing behind it so strongly and at this point you would need to show iperf to make me believe you have actually tested it on any device.

I can only report what i see, I will happily do some testing this weekend

Here is a thought, since USB4 gen2x2 is also 20Gbps maybe the firmware in my Diewu also implements this link mode besides the "normal" USB3 gen2x2

I'm not discussing iperf/driver performance, just the actual USB link layer