Framework's 10G Module Proves USB-C Has Too Many Speeds

Jeff Geerling spent a week with WisdPi's new 10G Ethernet Expansion Card for Framework laptops and found the same product delivering three different real-world speeds depending on which Framework laptop he used, which OS he ran, and which Realtek driver the kernel could compile. The card is rated 10 Gbps. On a Framework 13 with AMD's Ryzen AI 5 340, it delivered 9.4 Gbps on Windows 11 and noticeably less on Linux. On a Framework 12 with a 13th-gen Intel chip, the same card delivered 7 Gbps in Linux even though lsusb reported a 20 Gbps link. The story is not "Framework made a bad product." USB-C's bandwidth tiers — Gen 2x2, Gen 2x1, USB4, and the tunneling modes underneath — have become so layered that a single $99 dongle can be advertised as 10 Gbps and delivered as 7, 9.4, or 10 depending on factors the buyer cannot inspect at purchase time. The post is a hardware review. The lesson is about software.

What the WisdPi 10G card actually delivered

Geerling's setup, pulled from the published post:

• The card: WisdPi's 10G Ethernet Expansion Card, which fits any Framework Expansion slot including the Framework Desktop. It uses the Realtek RTL8159, which needs USB 3.2 Gen 2x2 (20 Gbps of raw bus bandwidth) to hit the rated 10 Gbps.
• Framework 13 (AMD Ryzen AI 5 340): Windows 11 delivered 9.4 Gbps on average. Linux was "slightly worse." Framework's port documentation says Gen 2x2 should be supported on at least ports 1 and 3 — but only in the sense that the bus is capable, not that any specific accessory will land on it.
• Framework 12 (13th-gen Intel mobile): Linux reported a 20 Gbps link via lsusb and delivered 7 Gbps in iperf3. The Realtek out-of-tree driver failed to compile on Ubuntu 26.04 because the bundled Linux 7.x kernel is newer than the driver expects. Windows 11 with the in-box driver delivered the same 7 Gbps; the vendor Realtek driver pushed unidirectional throughput to 9.4+ Gbps (with a bidirectional mix of ~9 Gbps up and 4–5 Gbps down).

Geerling's own recommendation at the bottom of the post: most people should buy the regular 2.5 Gbps Ethernet Expansion Card for $40 and stop there. The $99 10G card is the right answer only if you specifically need more than 2.5 Gbps and specifically do not want an external USB-C dongle. As of the post's publication on 24 June 2026, the 10G card was out of stock.

The five angles that actually matter

1. USB-C is a stack of five buses with overlapping names

The reason the same $99 product can deliver 7 Gbps, 9.4 Gbps, or 10 Gbps on the same laptop line is that "USB-C" is the connector, not the protocol. The protocols on that connector are at least five distinct things: USB 3.2 Gen 2x1 (10 Gbps), USB 3.2 Gen 2x2 (20 Gbps), USB4 (20 or 40 Gbps, mandatory tunneling), USB4 v2 (80 Gbps, optional), and Thunderbolt 3/4 (40 Gbps). The RTL8159's 10 Gbps Ethernet only fits inside the 20 Gbps tier. Many Framework laptops ship with USB4 ports that the chipset routes through a USB 3.2 Gen 2x1 tunnel in some configurations — at which point the RTL8159 is bandwidth-starved and the user sees ~7 Gbps, regardless of what lsusb says.

This is the same family of measurement disagreement the blog covered with the Google IPv6 vs APNIC numbers earlier this month: two endpoints measuring different things and both correct, and a buyer who cannot tell which measurement applies to their own port.

2. The Realtek driver situation is the real story

Geerling's headline is "USB-C is complex." The deeper story is that the Realtek RTL8159 needs an out-of-tree driver on Linux and a vendor driver on Windows, and neither is in great shape. On Ubuntu 26.04 with the 7.x kernel, the driver did not compile. On Windows 11 with the in-box Microsoft driver, throughput was 7 Gbps. Only Windows with the Realtek driver delivered the 9.4+ Gbps the silicon can do. If you buy a 10G USB-C Ethernet adapter in 2026 and run it on Linux, expect to either pin an older kernel, build the Realtek driver yourself, or accept the unidirectional throughput gap Geerling measured (roughly 7 Gbps on Linux vs. 9.4+ on the vendor driver — about a 25% drop).

The throughput gap is the same shape as the Codex log-write-amplification story this blog covered: the silicon can do the rated thing, the rated thing requires a specific driver + kernel + chipset combination, and the user discovers the gap the first time the workload hits the bottleneck. The pattern is "the spec is real, the floor under the spec is not."

3. The 70°C plastic surface is the spec nobody wants to talk about

The most under-reported part of Geerling's post is the thermal result. After running the card at full bidirectional load, the bottom plastic surface reached ~70°C. WisdPi told Geerling the surface is in compliance with IEC 62368-1, which permits sustained skin contact at that temperature for up to 10 seconds. Geerling's response — the right one — is that this is a laptop, and laptops are routinely used on laps. The 10G power and thermal budget was designed assuming a chassis with airflow, not a slot dissipating into a sealed aluminum unibody with a user sitting on top of it. The expansion-card slot, in other words, is a thermal compromise the buyer absorbs by reading the spec sheet — a casual way to add 10G to a laptop it is not.

4. "Sticks out like a sore thumb" is a real design constraint

The HN thread (226 points, 117 comments, submitted 26 June) is heavily weighted toward the form-factor question. petterroea's top-rated comment makes the case bluntly: Framework should have shipped a flush 1 GbE module first, because that use case is the one that actually fits a laptop. A flush 10 GbE card is mechanically impossible without active cooling; a protruding 10 GbE card is what the Framework 12/13/16 form factor actually delivers. jeffbee's comment makes a more useful technical point: for the 10G laptop-to-laptop use case, a Thunderbolt cable between the two computers is what jeffbee recommends (acknowledging the cable is admittedly pricey). The WisdPi card's real customer, in my reading, is a desktop user who wants a clean front-panel 10G jack — the 10G-to-laptop use case is better served by a cable than a card.

5. The 10G Ethernet dongle market is converging on the same constraint

Geerling's earlier "New 10 GbE USB adapters are cooler, smaller, cheaper" post tracked the wave of USB-C 10G adapters that landed in late 2025 and early 2026. Every one faces the same constraint: the silicon is ready, the drivers are mostly there, the chassis fits a laptop bag, and the bus they plug into is a five-way compatibility lottery. The 10G Ethernet-on-USB market in 2026 is in the same place the 1G Ethernet-on-USB market was in 2012: working, but only if the buyer reads the chipset list carefully. The "10G" label is a ceiling, not a guarantee.

What this means for you

If you are buying 10G USB-C Ethernet in 2026, the chipset is the spec that matters. Realtek RTL8159 and RTL8157 are the current 10G USB controllers. Aquantia AQC111U is the older alternative with better driver support on older Linux kernels but harder to find new. Avoid adapters built on the RTL8156 (2.5G only) or the older Aquantia AQC100/107, which tops out at 5G. The 10G label on the box is meaningless without the chipset on the spec sheet. On Linux, pin to a kernel the Realtek driver compiles against, build the driver yourself, or accept the ~25% unidirectional throughput gap Geerling measured. The Framework expansion-card slot does not exempt you from any of this. The 2.5 Gbps Ethernet Expansion Card ($40) is the right default. The 10G card ($99) is the right answer only for a specific use case.

What to do this week

# 1. Check what USB-C tier your laptop exposes on each port
#    (Linux: find the bus number from `lsusb -t`)
lsusb -t
lsusb -v -d XXXX:XXXX 2>/dev/null | grep -i 'bcdUSB\|bInterfaceClass'

# 2. Verify the Ethernet adapter's controller
ethtool -i eth1 | grep -E 'driver|bus-info'

# 3. Test the actual ceiling (start iperf3 server first)
iperf3 -s
iperf3 -c <server-ip> -t 30 -P 4

# 4. For Realtek RTL8159, check the in-tree driver status
modinfo r8159 2>/dev/null && echo "in-tree driver present" || echo "needs out-of-tree Realtek driver"

The bottom line

The Framework 10G Expansion Card is a useful product that exposes a real problem. It works when the bus, chipset, driver, and chassis all line up. "The bus" is five different things, the driver story on Linux is a quarterly coin flip, and the chassis thermal budget assumes a desktop. The buyer pays for the 10G ceiling; the buyer does not pay for the work of making the ceiling land in practice. Until USB-C gets a single, enforced naming convention — and there is no industry momentum toward that — the chipset list is the spec, and the rest is marketing.

Disclosure

This post was drafted with AI assistance. The primary source (Jeff Geerling's blog post) was fetched directly via curl --compressed and re-read. The HN thread context (226 points, 117 comments, item id 48681220) and the six cited HN comment permalinks (kelnos 48681498, RachelF 48681539, jeffbee 48682254, petterroea 48682324, purpleidea 48682362, drnick1 48682527) were verified id-to-author against the HN Algolia API at 21:00 UTC+8 on 26 June 2026. All quantitative claims about the WisdPi card (9.4 Gbps on Windows, 7 Gbps on Linux, ~70°C plastic surface, $99 / $40 pricing, "out of stock as of publication") are reproduced from Geerling's post. The author's "the unit I tested was sent to me by WisdPi for testing and review" note is reproduced; this is a material conflict-of-interest disclosure on Geerling's part. The Realtek / Aquantia chipset taxonomy is general industry knowledge cross-checked against the Linux kernel drivers/net/usb/ tree. The WisdPi product page on wisdpi.com was not retrievable as a stable product URL at review time (the sitemap has no deep link for the Framework 10G card); wisdpi.com is cited as the company root. The IEC 62368-1 10-second skin-contact claim is paraphrased from the WisdPi statement as reported by Geerling; the standard's text appears as a paraphrase rather than a direct quote. The "jeffbee recommends Thunderbolt" framing is faithful to the comment's substance but adds author editorial context on why Thunderbolt beats the WisdPi card for laptop-to-laptop use. The "four expansion ports" count in an earlier draft was corrected to the source's specific "ports 1 and 3" framing. The ~25% throughput figure is derived from Geerling's 7 Gbps / 9.4+ Gbps measurements. The author's editorial position (the "chipset is the spec" framing, the "Framework slot does not exempt you from the bus lottery" take, the Thunderbolt counter-recommendation) is the author's.

Sources

• Jeff Geerling, "Framework's 10G Ethernet module exposes USB-C's complexity", jeffgeerling.com, 2026-06-24 — primary source for all WisdPi card benchmarks, the Framework 13/12 test results, the Realtek driver situation on Linux and Windows, the ~70°C plastic-surface thermal reading, the IEC 62368-1 statement, and the $99 / $40 / out-of-stock price/availability figures.
• Hacker News discussion thread for "Framework's 10G Ethernet module exposes USB-C's complexity" (item 48681220, submitted 2026-06-26, 226 points / 117 comments as of 26 June 2026 21:00 UTC+8) — secondary source for the form-factor critique, the "stuck out like a sore thumb" thread consensus, and the Thunderbolt counter-recommendation. The 226 / 117 figures were verified live via the HN Algolia API at review time.
• WisdPi company root, wisdpi.com — vendor source for the 10G USB Network Adapter and the Realtek-based product line; the specific Framework 10G Expansion Card product page was not retrievable as a stable URL on wisdpi.com or its sitemap at review time (the product is sold direct via Amazon and through Framework's marketplace; the canonical vendor page link in the source post points to wisdpi.com but the deep link was not resolvable).
• Realtek RTL8159 / RTL8157 / RTL8156 driver repository — context for the Linux driver situation.
• USB 3.2 specification, USB-IF — context for the Gen 2x1 (10 Gbps) / Gen 2x2 (20 Gbps) naming convention.