The Differences Between USB 4.0 and Thunderbolt 4

1. Technical foundation
USB4.0: Based on Intel's Thunderbolt 3 protocol, it was developed by USB-IF (USB Developers Forum). It inherits some features of Thunderbolt 3, but is not exactly the same.

Thunderbolt 4: Led by Intel, it is an upgraded version of Thunderbolt 3, compatible with some features of USB4.0, but has stricter technical requirements and additional functions.

2. Data transfer rate
USB4.0: Supports a maximum transfer rate of 40Gbps (in dual-channel mode), the same as Thunderbolt 3. However, the actual rate may vary depending on the device and the protocol supported.

Thunderbolt 4: Also supports a maximum transfer rate of 40Gbps, but requires all ports to support 40Gbps, while some implementations of USB4.0 may only support 20Gbps.

3. Compatibility
USB4.0: Downward compatible with older standards such as USB 3.2 and USB 2.0, and supports Thunderbolt 3 devices (but not mandatory).

Thunderbolt 4: Fully compatible with Thunderbolt 3 and USB4.0 devices, and also supports USB 3.2, USB 2.0, etc.

4. Video output
USB4.0: Supports the DisplayPort 1.4a protocol, capable of outputting 8K resolution (60Hz) or dual 4K resolution (60Hz).

Thunderbolt 4: Also supports DisplayPort 1.4a, but requires at least dual 4K resolution (60Hz) or single 8K resolution (30Hz).

5. Power supply and charging
USB4.0: Supports the USB PD (Power Delivery) protocol, capable of providing up to 100W of power.

Thunderbolt 4: Also supports USB PD, but requires at least 15W of power (for charging connected devices), while Thunderbolt 3 has no such requirement.

6. Expansion functions
USB4.0: Supports PCIe tunneling technology (for external graphics cards and other devices), but the specific implementation depends on the manufacturer.

Thunderbolt 4: Requires support for PCIe tunneling technology and provides more stable performance, suitable for external graphics docking stations, high-speed storage, and other scenarios.

7. Security
Thunderbolt 4: Introduces DMA protection based on Intel VT-d (to prevent malicious devices from attacking the system through direct memory access), while USB4.0 has no such mandatory requirement.

8. Application scenarios
USB4.0: More suitable for general scenarios, such as external storage, displays, and ordinary peripherals.

Thunderbolt 4: Designed for high-performance requirements, such as professional video editing, external graphics cards, multi-display workstations, etc.

Summary
USB 4.0 and Thunderbolt 4 are highly similar in technology, but Thunderbolt 4 has stricter requirements in terms of performance, compatibility and functionality, making it more suitable for professional users. Ordinary users can meet their needs by choosing USB 4.0, while users requiring high-performance expansion capabilities should give priority to Thunderbolt 4.