USB4 and Thunderbolt: How They Differ from Ordinary USB-C, What They Can Do and Why One Cable May Not Work

The USB-C connector was supposed to make life simple: one universal oval port for everything — data, charging, monitors. In practice it created one of the most confusing situations in computing. Ports and cables look identical, yet some carry video and others don't; some charge a laptop and others only a phone; some copy files at 40 Gbit/s and others at the speed of a decade-old flash drive. Let's look at how USB-C, USB4 and Thunderbolt differ and how to tell what your port and cable can do.

USB-C is a shape, not a set of capabilities

The main thing to remember: USB-C is only the shape of the connector. What a port can actually do depends on the standard behind it and on what the maker of that particular laptop implemented. Behind an identical connector there may be slow USB 2.0, fast USB 3.2, USB4 or Thunderbolt.

The main standards

• USB 2.0 over USB-C — up to 480 Mbit/s. Found in cheap charging cables and on some phones.
• USB 3.2 Gen 1 / Gen 2 / Gen 2x2 — 5, 10 and 20 Gbit/s. Enough for external SSDs and most peripherals.
• USB4 — 20 or 40 Gbit/s, with support for video output and complex docking stations. USB4 version 2.0 — up to 80 Gbit/s.
• Thunderbolt 3 and 4 — 40 Gbit/s. Thunderbolt 4 guarantees a minimum feature set: two 4K monitors, charging and connecting external PCIe devices. Compatible with USB4.
• Thunderbolt 5 — up to 80 Gbit/s, and up to 120 Gbit/s for displays in certain modes. Needed for very demanding work.

What fast ports can do

• Connect monitors — via DisplayPort Alternate Mode or tunnelled over USB4/Thunderbolt. One port can drive one or two external monitors.
• Charge a laptop (Power Delivery) — up to 100 W, and up to 240 W under newer versions of the standard. But not every laptop port accepts charging.
• Docking stations — one cable from the laptop provides monitors, networking, USB ports and charging.
• Fast external SSDs — USB4/Thunderbolt drives run at nearly the speed of an internal drive.
• External graphics cards — over Thunderbolt/USB4 you can connect an enclosure with a desktop graphics card, though with some loss of performance.

How to find out what a port can do

There are often symbols next to a laptop's port: a lightning bolt for Thunderbolt, a D or monitor icon for video output, a battery or plug icon for charging, and "10" or "40" markings for speed. But many manufacturers don't add symbols. The most reliable way is to check the specifications of your exact model on the manufacturer's website. Laptops often have two identical ports, only one of which supports video and charging.

Cables differ too

The USB-C cable that came with your phone often supports only USB 2.0 and low-power charging. A monitor, dock or fast SSD needs a cable of the matching standard: marked 40 Gbit/s, Thunderbolt or USB4. Charging laptops above 60 W needs a cable with a 100 W (5 A) or 240 W chip. Long passive cables work less well at high speeds — longer distances need active cables. Many "inexplicable" monitor and dock problems are solved simply by changing the cable.

Common problems

• The monitor shows no picture over USB-C — the port doesn't support video output, the cable is charge-only, or the graphics/Thunderbolt driver is outdated.
• The dock only partly works — incompatible standards, not enough bandwidth for two high-resolution monitors, or the dock firmware or laptop BIOS needs updating.
• The laptop says "slow charging" — the charger, dock or cable doesn't deliver enough power.
• A Thunderbolt device isn't detected — the device needs authorising, or the driver and firmware need updating.
• An external SSD is slow — it's connected through a slow cable, hub or port.

Do you need Thunderbolt or USB4?

If you connect one monitor and a couple of devices to your laptop, ordinary USB-C with video output is enough. USB4 or Thunderbolt is worth having if you run two monitors over one cable, edit video from fast external SSDs, or use a powerful dock or external graphics card. When buying a new work laptop, at least one USB4/Thunderbolt port is a good investment in the future.

What our technician does

1. Finds out what the ports on your laptop or computer can do.
2. Selects compatible cables, docking stations, adapters and external drives.
3. Updates drivers, Thunderbolt firmware, the BIOS and dock firmware.
4. Connects and sets up monitors, screen arrangement, resolution and refresh rate.
5. Diagnoses charging and video output problems over USB-C.

A real example

An architect in Saburtalo bought a dock so he could connect two monitors, a keyboard and the network to his laptop with a single cable. Only one monitor worked, and the laptop complained of slow charging. Our technician found the dock was plugged into a laptop port that only supported data, using the cable that came with a phone. We connected the dock to the Thunderbolt port with the right cable and updated the dock firmware and drivers. Both monitors now run at full resolution, and the laptop charges at full power.

Call a technician

If a monitor won't connect over USB-C, a dock isn't behaving or you need a workspace set up, we'll come to any district of Tbilisi around the clock. Learn more on our computer setup, driver installation and laptop diagnostics pages.