USB-C E-Marker Claims Can Mislead: How Windows Users Verify 240W, USB4 and Thunderbolt Cables

A recent hands-on investigation by XDA Developers writer Shivansh Raj Srivastava peeled back the curtain on this exact problem by reading the electronic marker (e-marker) chips inside three everyday USB-C cables. The findings serve as a wake-up call for PC builders, laptop owners, and IT administrators alike: not only can product packaging make claims a cable was never certified to meet, but the tiny chip inside the plug is merely a digital declaration—one that only repeats whatever a factory flashed onto it.

What Is an E-Marker Chip, and Why Does Your PC Care?​

To understand how a cable can misrepresent its pedigree, you first have to understand how modern USB-C negotiation works. Under USB-IF specifications, any USB-C cable rated to carry more than 3 amps of current (anything beyond 60W of power) or high-speed data links like 40Gbps USB4 and Thunderbolt must contain an electronic marker chip, commonly known as an e-marker.

When you plug a cable into a host computer, the port feeds a tiny power rail called VCONN into the cable's plug and issues a USB Power Delivery (USB-PD) "Discover Identity" request. The e-marker answers with Vendor Defined Objects (VDOs)—essentially a 128-bit digital passport containing four 32-bit fields:

• ID Header: Identifies the vendor and whether the cable supports alternate modes (such as Thunderbolt or DisplayPort).
• Certification ID (XID): The compliance identifier assigned by the USB Implementers Forum (USB-IF) if the cable passed official testing.
• Product ID: The manufacturer's specific product identifier and firmware revision.
• Cable VDO (Record): The specific electrical and data claims, including maximum voltage (such as 20V, 48V, or 50V), current handling (3A or 5A), cable length class, and top data signaling speed (from USB 2.0 up to USB4 Gen 3 at 40Gbps or beyond).

Your Windows 11 laptop, Mac, or charger reads this digital passport before deciding how much wattage to push down the copper or which high-speed data lanes to initialize. If no e-marker responds, a compliant host assumes it is dealing with a basic cable and caps charging power at 3A and 60W for safety, even though data lanes can still run at high speeds if the physical wires are present.

The critical catch? An e-marker is not an active diagnostic tool or a physical stress test. As developer Darryl Morley notes in the documentation for his open-source inspection tool WhatCable, software cannot verify what is physically inside the cable jacket; it only reads what the chip claims.

Inside the Three-Cable Investigation: When Twins Tell Different Stories​

In the XDA Developers test, Srivastava used an Apple Silicon M2 MacBook Air, a Samsung T7 Shield portable SSD, and the macOS utility WhatCable to interrogate three different cables: the Portronics Flash C2 (sold for around $10), the budget Portronics Konnect 240C (under $4), and the short USB-C cable bundled in the box with the Samsung T7 Shield. Because Mac ports often wait to power the VCONN rail until a partner device is attached on the far end, connecting the Samsung SSD forced the host to query the cables' e-markers and negotiate an active data link.

Here is how the three cables stacked up according to the XDA Developers report:

At first glance, the budget Konnect 240C and the bundled Samsung cable behaved exactly as expected. The Konnect 240C is marketed as a heavy-duty 240W charging cord with slow USB 2.0 data, and both its chip and its 480Mbps transfer rate reflected that. Samsung's short drive cable lacked an e-marker entirely—meaning a laptop would restrict it to 60W charging—but because it possesses the necessary SuperSpeed wires, it effortlessly ran the T7 Shield at the drive's maximum 10Gbps interface ceiling.

The intrigue centered on the Portronics Flash C2. Its retail box boldly advertises "Thunderbolt 4.0," alongside 40Gbps speeds and 240W charging (a claim echoed on Portronics' official product page for model POR 2802, which markets the cord as a "USB 4 Thunderbolt 4" cable rated for 240W at 48V/5A and 8K/60Hz video). When queried by WhatCable, the Flash C2's e-marker chip reported USB4 Gen 3 at 40Gbps and 50V at 5A.

However, when Srivastava pulled the raw register data via the macOS terminal command ioreg -r -w0 -c IOPortTransportComponentCCUSBPDSOPp, the relationship between the $10 Flash C2 and the sub-$4 Konnect 240C came into sharp focus. Across the 128 bits of identity data returned by both Portronics cables, the two chips were virtually identical twins, differing by just three bits:

1. The Speed Field: In the cable record byte, a hexadecimal value shifted from 40 on the Konnect 240C to 43 on the Flash C2, changing the declared speed ceiling from USB 2.0 to USB4 Gen 3 (40Gbps).
2. The Alternate Mode Flag: In the ID header byte, a value shifted from 18 to 1c, flipping the flag that tells a host computer the cable supports extra modes like Thunderbolt.

Every other bit in the two chips matched. Both reported a Vendor ID of zero, a USB-IF Certification ID of zero, and a Product ID of zero. Even more telling, both chips reported the exact same internal cable-length class—roughly two meters—despite the cables being sold at around 1 to 1.25 meters.

Why "USB4 40Gbps" Is Not the Same as "Thunderbolt 4"​

Does a zeroed-out Vendor ID or an uncertified chip automatically mean the Portronics Flash C2 is a fake that cannot carry fast data? Not necessarily. As both XDA Developers and the WhatCable documentation point out, USB-IF certification is voluntary, and plenty of functional cables—including some from major brands—ship with blank fields or uncertified IDs. Moreover, because the Samsung T7 Shield tops out at 10Gbps, the test could only confirm that the Flash C2 handles at least 10Gbps data and high-wattage charging; testing its true 40Gbps ceiling would require a native 40Gbps USB4 or Thunderbolt drive or dock on the far end.

Where the packaging crosses the line is the "Thunderbolt 4.0" claim.

Unlike generic USB speed tiers, Thunderbolt 4 is an Intel-developed standard with mandatory certification requirements for all shipping PCs, accessories, and cables. According to Intel's official Thunderbolt 4 documentation, certification guarantees constant 40Gbps bandwidth dynamically allocated between data and video, support for dual 4K 60Hz displays (or one 8K 60Hz display), PCIe data tunneling, and strict signal-integrity compliance up to two meters.

In the case of the Flash C2, the red flags piled up quickly:

• No Official Directory Listing: Certified products are listed in Intel's official Thunderbolt product directory, and Srivastava found no listing for Portronics.
• Missing Connector Logos: Genuine Thunderbolt 4 cables are required to bear the official Thunderbolt lightning logo and number on the connector housing. The Flash C2's plugs were instead etched with generic "USB4.0" and "240W 40Gbps 8K60Hz" text.
• Non-Standard Naming: The box printed "Thunderbolt 4.0"—a decimal version naming scheme Intel does not use.
• Spec Contradictions: The physical packaging and online product listings couldn't even agree on the physical build; XDA Developers noted the retail box claimed a 1.25-meter cotton-braided cord, whereas Portronics' website lists a 1-meter nylon-braided cable.

In short, slapping "Thunderbolt 4" on a box when the product is at best an uncertified USB4 cable is a classic marketplace bait-and-switch.

Why This Matters for Windows 11 and Enterprise IT​

If you are running a modern Windows 11 workstation—especially an Intel Evo or vPro laptop, an AMD Ryzen AI system with USB4, or a Qualcomm Snapdragon X Elite Copilot+ PC—cable quality is the thin line between a seamless desk setup and a troubleshooting nightmare.

Microsoft integrated native USB4 and Thunderbolt connection management directly into Windows 11, bringing driver support from the firmware level into the operating system and adding native controls under Settings > Bluetooth & devices > USB > USB4 Hubs and Devices. When you plug a laptop into a Thunderbolt 4 dock driving two 4K monitors, a 2.5GbE network adapter, and an NVMe scratch disk, Windows relies on the USB-PD handshake and the cable's physical shielding to maintain high-frequency PCIe and DisplayPort tunnels.

When an uncertified cable's e-marker claims 40Gbps and alternate-mode support, your Windows 11 host will take it at its word and attempt to establish a full 40Gbps link. If the copper wiring and shielding inside the jacket cannot actually sustain those frequencies without signal degradation, you won't always get a clean error message. Instead, you get the classic ghosts of the IT helpdesk:

• External monitors that randomly flicker black for two seconds when the GPU load spikes.
• Thunderbolt docks that drop their USB audio or Ethernet connections until unplugged.
• External NVMe SSDs that silently fall back to 10Gbps or disconnect mid-transfer, corrupting file writes.
• High-wattage 140W or 240W Extended Power Range (EPR) chargers that either fail to negotiate full speed or push 5 amps through under-spec conductors.

How to Audit Your USB-C Cables on Windows and Mac​

You do not need an electrical engineering degree or a five-figureKeysight vector network analyzer to keep dishonest cables out of your gear bag. Whether you use Windows or macOS, here is how to verify what you are plugging into your machine:

1. For Windows PC Users: Hardware Testers and Built-In Diagnostics​

Unlike Apple Silicon Macs, which expose raw near-end (SOP') and far-end (SOP'') e-marker data objects through public IOKit registry paths, standard Windows x86 and ARM USB controllers do not consistently expose raw e-marker hex dumps to user-space software without specialized hardware. (In fact, even Intel-based Macs cannot run WhatCable because Intel's Titan Ridge Thunderbolt controllers do not expose those USB-PD VDOs through public OS accessors.)

• Use a Dedicated USB-C Protocol Meter: As noted in XDA Developers' testing, the gold standard for Windows users and IT benches is an inline hardware tester such as ChargerLAB's Power-Z KM003C (or similar inline e-marker readers from brands like FNIRSI or Plugable). You simply plug the cable into the meter, and its screen decodes the e-marker's exact VDO fields, showing declared voltage, amperage, USB4/Thunderbolt mode flags, and Vendor IDs independent of your OS.
• Check Windows 11 USB4 Settings: When you connect a USB4 or Thunderbolt device on Windows 11, open Settings > Bluetooth & devices > USB to inspect your connected USB4 hubs and devices, or use diagnostic utilities like USB Device Tree Viewer (UsbTreeView) to verify the actual negotiated link speed (such as SuperSpeedPlus 10Gbps vs. 20Gbps or 40Gbps) when a known high-speed device is attached.

2. For Apple Silicon Mac Users: WhatCable and Terminal​

If you have an M1, M2, M3, or M4 Mac running macOS 14 (Sonoma) or later in your toolkit, you can read e-marker chips directly for free:

• Install the open-source menu bar utility via Homebrew using brew install --cask darrylmorley/whatcable/whatcable.
• Remember to plug a device or charger into the far end of the cable so the host powers the VCONN rail and queries the chip (and on Mac mini or Mac Studio desktops, use the rear Thunderbolt ports rather than the front hub-routed USB-C ports).
• To view the raw 32-bit hexadecimal identity records directly in Terminal, run ioreg -r -w0 -c IOPortTransportComponentCCUSBPDSOPp.

3. The Three-Step Buyer's Checklist​

Before buying your next high-speed or high-wattage cord, apply three simple rules:

1. Verify the Logos on the Plug: As the USB-IF compliance program mandates, certified USB-C cables must be clearly marked with their power capability (60W or 240W) and data rate (such as 20Gbps or 40Gbps). Genuine Thunderbolt 4 cables will always carry the official Thunderbolt lightning icon on the connector housing itself, not just a "Thunderbolt compatible" blurb on the retail box.
2. Check Official Directories: If you are paying a premium for Thunderbolt 4 reliability, verify the brand and model in Intel's official Thunderbolt Product Directory or the USB-IF Certified Product Search.
3. Separate Power Claims from Data Speeds: Never assume a "240W E-Marker" cable is fast at moving files. As the Portronics Konnect 240C proved, a cable can legitimately carry a 240W (48V/5A) e-marker for laptop charging while physically wiring only USB 2.0 data pins that top out at 1990s-era 480Mbps speeds.

An e-marker chip is a useful convenience, not a lie detector. Treating it as a claim to be verified—rather than a guarantee of performance—will save your ports, your peripherals, and your sanity.