Thunderbolt™4 Test

Thunderbolt™ 4 Technology Overview
Following the Thunderbolt™ 3 technology, Intel launched Thunderbolt™ 4, which is integrated into the new notebook Tiger Lake processor. The Thunderbolt™ 4 technology architecture and the USB4™ protocol specification are essentially one family. Both are based on the Thunderbolt™ 3 architecture. Both have a maximum transfer rate of 40Gbps (20G x2) and support Thunderbolt™ 3 and USB4™. The main purpose is to combine multiple protocols into the same channel, including protocol signals such as USB 3.2, DisplayPort, and PCIe, which can be used for simultaneous audio-visual and data transmission through a USB Type-C cable. In Intel’s latest Thunderbolt™ 4 Functional Test Specification (FV CTS), USB4™ device has been added to the test project and related test methods have been updated.


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What is the difference between Thunderbolt™ 4 & USB4?

Thunderbolt™ 4 and USB4™ are functionally complementary and compatible

Thunderbolt™ 4 focuses on the application of PC and its peripheral devices; USB4™ function applications are not only used in PCs, but also in mobile phones and Embedded Hosts.

Taking PC as an example, the following table lists the minimum requirements that Thunderbolt™ 4 and USB4™ must support.

You can clearly find that Thunderbolt™ 4 is equipped with many functions as a standard, but USB4™ is mostly optional

*USB4™ products can choose whether to support Thunderbolt Compatible (10.3125G & 20.625G)


Certification area 

Type and examples of Thunderbolt™ 4 certified products



Thunderbolt™ 4 test process (same as Thunderbolt™ 3)

The product information sheet of the test object must be provided before the test:

TBT4 and TBT3 test process



Thunderbolt™ 4 Test Content

Reference test instrument list


Thunderbolt™ 4  full-service plan

GRL provides a complete Thunderbolt™ 4 electrical automated test solution to facilitate product verification and reduce the test burden for the verification unit.
The following FAQ explains: In terms of electrical test (Electrical Test), the current Thunderbolt™ 3, Thunderbolt™ 4 and USB4™ electrical tests are all tested according to the same test specification ( USB4 Electrical CTS )

The GRL software can support  Thunderbolt™ 4/ USB4™/ Thunderbolt™ 3 tests at the same time . This solution provides the same verification tools as the laboratory and can help your company improve its self-verification capabilities


Thunderbolt™ 4  Technical Article 

Topic: Interpretation of Transmitter Preset Calibration in USB4™ and Thunderbolt™ 4 Certification Test

Strict electrical test specifications will individually set the optimal initial signal for each USB4™/Thunderbolt™ 4 product output signal quality, so that the USB4 product can be quickly connected and communicated as soon as it is connected. That is, Transmitter Preset Calibration (hereinafter referred to as Tx Preset Cal) in the electrical test specification.

It is stated in the USB4 specification that the high-frequency output terminal needs to support 16 sets of Presets (default values) as shown in the table below, which means that there are 16 sets of outputs with different signal quality. In the USB4 electrical signal certification test, which set of Preset should be used for testing to ensure the quality of the output signal? Or 16 sets of Presets all tested? Reference article full text…


Other related FAQ

1.. Is there any difference between the Electrical Test test items and test specifications of Thunderbolt™ 4 & USB4™

  • As far as Electrical Test is concerned, it is the same. At present, Thunderbolt™ 3, Thunderbolt™ 4 and USB4™ electrical tests are conducted in accordance with the same test specification ( USB4 Electrical CTS ).
    • Thunderbolt™ 4 test needs to include Data Rate 10.0G, 20.0G, 10.3125G, and 20.625G
    • USB4™ test needs to include Data Rate 10.0G & 20.0G. If the product is compatible with Thunderbolt™ 3, the 10.3125G and 20.625G items need to be tested
  • In the part of VBus/Vconn power supply, Thunderbolt™ 4 and USB4™ have different requirements.


2.  In addition to the Electrical Test, what are the differences between Thunderbolt™ 3 & USB4™ tests

The only test item for Thunderbolt™ 4 and USB4™ is the Electrical Test. The rest of the test items are slightly different as follows. Please follow the product announcement to support Thunderbolt™ 4 or USB4™ for certification testing.

  • Thunderbolt™ 4 certification test : Electrical + Functional/IOP test
  • USB4™certification test : Electrical + Functional/IOP + Protocol + Logical Layer + TMU + Tunneling test supported (參考Tunneling)


3. Do USB4 products compatible with TBT3 need to obtain Thunderbolt™ 4 & USB4™ certification at the same time?

No need to. USB4™ products compatible with Thunderbolt™ 3 only need to obtain USB4™ certification in accordance with the requirements of the USB Association. Only need to add Thunderbolt™ 3  related test items.


Please consult for technical consultation and testing services

USB4™, USB, USB-C®, USB Type-C® and USB-IF are registered trademarks of USB Implementers Forum

Intel, Thunderbolt™ 3 and Thunderbolt™ 4 are registered trademarks and R&D products of Intel

This information is provided for reference only. This information is not and should not be regarded as an official communication of the USB Implementers Forum (USB-IF). The official communication of USB-IF can be  obtained from its website or directly from USB-IF.