Intel had officially announced Thunderbolt 4 at CES 2020 when it stated that the new interconnectivity standard would be supported by Intel's upcoming Tiger Lake platform. However, most of the specifications around Thunderbolt 4 were shrouded in mystery until today's announcement. We now know that Thunderbolt 4 isn't any faster than Thunderbolt 3, which had a bandwidth of 40 Gbps, rather it raises the bare minimum requirements for certification, expands the feature set and adds compliance with the USB4 specification since Thunderbolt 4 will use the USB Type-C connector. Also announced today are the new 8000 series of Thunderbolt 4 connectors that will be available later this year. The new controllers include the JHL8540and JHL8340 host controllers for computer makers, and the JHL8440 device controller for accessory makers.
Typical Thunderbolt dock
“Thunderbolt provides consumers with a leadingconnectivity standard across a range of devices,helping to advance computing experiencesanddelivering on the promise of USB-C withsimplicity,performanceandreliability. The arrival of Thunderbolt4underscoreshow Intel is advancingthe PC ecosystem toward truly universal connectivitysolutions.”–Jason Ziller, Intel general managerof theClient Connectivity Division
As stated previously, Thunderbolt 4 is an expansion of the existing Thunderbolt 3 protocol with the intent on expanding its feature set. Thunderbolt 4 will still provide the same 40 Gbps bandwidth as Thunderbolt 3 over a single connection while using the USB Type-C connector. It now has compliance with USB4 whereas Thunderbolt 3 was merely compatible with USB 4.
Intel Thunderbolt 4 certification requirements and specifications
The difference is that in the latter case, one would operate the the least common denominator whereas with full compliance, Thunderbolt 4 will give you the proper rated experience. Thunderbolt cables can now be up to 2 meters in length and requires support for two 4K displays (or one 8K display) and should be rated for PCIe 32 Gb/s to pass the certification tests. TB4 will enable support for docks with up to four Thunderbolt 4 ports.
A critical requirement for Thunderbolt 4 certification is Intel VT-d based DMA protection. From a security standpoint, this is geared towards helping prevent physical DMA attacks. However, it should be noted that VT-d is an Intel exclusive technology that allows guest systems to directly access a PCI device. AMD uses AMD-Vi for a similar effect but the two are distinct. This requirement would effectively make Thunderbolt 4 exclusive to Intel processors only. This is a form of vendor lock-in that is frowned upon in the industry but a common practice nevertheless. We've reached out to Intel for further clarity on the same.
UPDATE: Intel gave us the following statement, "Thunderbolt is open to non-Intel-based systems. Like any other system, devices must pass Thunderbolt certification and end-to-end testing conducted by third-party labs. Thunderbolt 4 requirements include Intel VT-d based or an equivalent DMA protection technology that provides IO virtualization (often referred to as IO Memory Management Unit or IOMMU), as well as OS implementation support. If the equivalent technology supports prevention against physical attacks, then that should meet the requirement."
Intel did not mention which other DMA protection technologies would fit the bill. AMD-Vi is a DMA protection technology but whether it would pass the certification remains unknown. We've reached out to labs that offer Thunderbolt 4 certification for further clarification.