Thunderbolt™ technology provides a fast interface solution for data transmission and peripheral connection. Thunderbolt™ is simple, faster, and multifunctional.


Let the Speed Do The Talking

Cable and connection technology is evolving at a fast rate. The advances relate to leaps of technological movement in other areas of consumer electronics. Modern technological development makes the need for cable technology further than the ordinary transfer of data to elevate user experience through speed, security, power, display and others.

Thunderbolt™ 4 Certification

Allion USA-SGS is authorized by Intel as one of the first test labs to provide certification testing for Thunderbolt™ products (Host). Intel first announced the 4th generation of Thunderbolt™ in 2019 and has officially opened certification testing of Thunderbolt™ 4 (Host) in Q2, 2020.

Thunderbolt™ 4 Structure

Thunderbolt™ 4 vs Thunderbolt™ 3 in terms of Host Products

The most significant difference between Thunderbolt™ 4 host (Intel platform) and others is that the Intel Thunderbolt4 Platform directly integrates Thunderbolt onto the CPU (SoC), while others still keep Thunderbolt™ IC discrete (Please refer to Table 1).

How is Thunderbolt™ 4 different from Thunderbolt™ 3

Table 1. Comparison between Thunderbolt™ 4 host and Thunderbolt3

According to Table 1, if Thunderbolt™ 4 host products use the Intel Platform, signals are directly transmitted from the SOC.  This poses a challenge for the layout of the motherboard if the trace length, which runs from Thunderbolt™ connector to CPU, needs to remain within 2 inches. In order to overcome the problem of trace length, a Re-timer is added between the CPU and Thunderbolt™ connectors to extend the signals.

Figure 1. Re-timer on Thunderbolt 4 Host

Re-timer IC contains CDR function, enabling simultaneous attenuation compensation while receiving and resending signals from the source. This CDR function can compensate the Thunderbolt™ trace length and effectively extend the signals.

Thunderbolt™ 4 Technologies

Thunderbolt™ 4 maintains the data rate at 40Gps, which is the same as Thunderbolt™ 3, but there is still a difference in the physical layers.

Thunderbolt™ 4, Thunderbolt™ 3, and USB4™

Next, we are going to address the difference between Thunderbolt™ 4, Thunderbolt™ 3, and USB4 to clarify the confusion frequently asked by developers and users.

Table 2. Thunderbolt 3, Thunderbolt 4, and USB4 Platform

Thunderbolt™ 4 Host Certification Process

Currently, Thunderbolt™ 4 host can undergo the official certification as long as the platform uses the CPU with QS stepping. The certification process is completely the same as Thunderbolt™ 3.

Figure 2. Thunderbolt 4 Certification Flow

Allion USA-SGS now offers Thunderbolt™ 4 Host Certification

We currently provide Thunderbolt™ 4 host and device certification testing. Well-trained engineers and testing instruments are ready to provide the services for our customers.

Thunderbolt™  4 Host Testing services include Electrical Validation (EV) & Functional Validation (FV) to validate signal integrity and interoperability of your products, respectively.

  • Electrical Validation (EV)
    • Stage 1. Pre-EV
    • Stage 2. EV Cert (CIO)
  • Functional Validation (FV)
Thunderbolt™ 4 Host EV Services
Thunderbolt™ 3 Thunderbolt™ 4
CIO Phy CIO Phy (New!)
USB3.X Phy USB3.X Phy
USB2 Phy USB2 Phy
DP Phy DP Phy
TBT3 Power TBT4 Power (New!)
PD3.0 PD3.0
Thunderbolt™ 4 Host FV Services
TBT3 Topologies TBT4 Topologies Cables Scenarios
TBT3 SPD TBT3 SPD Passive 40G Plug/Unplug
TBT3 BPD TBT3 BPD Passive 20G SX
USB3.X USB3.X Active TBT3 P2P
USB2 USB2 Active TBT4 (New!) NVM Update
eGFX eGFX Extended Tests
Monitors Monitors
TBT4/USB4 (New!)
Thunderbolt™ 4 Compliance Test Coverage
Pre-EV EV Certification FV Certification
. USB2.0 Electrical . TBT RX . Basic Host Functionality
. DP PHY (DP TX ALT Mode) . Return Loss . HDP
. USB-PD . System
. TBT Power . Docking
. RTD3 Support
. Interoperability

*Official test specifications are available

With our Thunderbolt™ 4 certification program and consulting service, we verify and validate cable devices against interoperability and compliance requirements of Thunderbolt™ 4 for:

  • Thunderbolt™ Certification: Through validation according to necessary compliance specifications.
  • Thunderbolt™ Pre-compliance Test: We help our customers perform pre-compliance tests which is a type of informal (sample) test before the actual certification test to identify potential issues or risks during certification.
  • Interoperability Test: For full compatibility with Thunderbolt and other devices.

We perform Thunderbolt™ testing services to verify and certify the device is compatible with a variety of Thunderbolt devices. Our test covers appliances, devices, and hosts with a variety of test categories on platform EQ, electrical validation, and functional validation.

USB4™ Host Certification

Thunderbolt™ 4 and USB4 interfaces are compatible in terms of the physical layer, but the two interfaces are certified by different standard associations. The following table shows the requirements for the two interfaces.

Certification Requirement between Thunderbolt™ 4 and USB4 Host

Thunderbolt™ 4 Device Certification

Allion USA-SGS is one of the first labs in the world to provide the certification of Thunderbolt™ 4 hosts and devices. Allion USA-SGS will be providing the full test service as well, please contact us at for more information regarding Thunderbolt™ 4 certifications.

Thunderbolt™ Certification Program

Thunderbolt™ Certification Testing

The Thunderbolt™ Certification Program aims to assist manufacturers in the design and development of devices that comply with Thunderbolt specifications. We provide compliance tests, performance tests, and other validations to ensure that Thunderbolt products create exceptional user experience through high-speed transmission and OS interoperability.

Thunderbolt™ Pre-compliance Test

Prior to the actual certification test, Allion USA-SGS assists customers in performing pre-test services to provide understanding of how a product measures against the actual certification test. With the same test environment and procedures as the actual certification test, our Thunderbolt technical consultants discover errors, find causes, and propose solutions to your product issues as well as facilitate the submission of certification applications.

Interoperability Test

In addition to standard certification tests, we can also provide you with the most comprehensive interoperability test services for different Thunderbolt™ devices, ensuring that your product is fully compatible with other Thunderbolt devices.


  • Host
    • Motherboard
    • Laptop
    • Add-In Card
    • All In One system
  • Device
    • Storage-Based Device
    • Laptop
    • Windows Device
  • Connector

 Test Coverage 

  • Pre-EV Tests – Host
    • X Phy
    • DP Phy
  • Electrical Validation – Host
    • CIO TX
    • CIO RX
    • CIO Return Loss
    • USB-PD
    • TBT Power
  • Functional Validation – Host
    • Windows FV CTS
  • Pre-EV Tests – Device
    • All the related electrical tests (USB, DP, HDMI, RJ45, SD)
    • Power related
  • Electrical Validation – Device
    • CIO TX
    • CIO RX
    • CIO Return Loss
    • USB-PD
    • TBT Power
    • PHY
    • DP PHY
  • Functional Validation – Device
    • Mac FV CTS & Windows FV CT

For more inquiries about the Thunderbolt™ testing service, please contact us.