Wired connectivity is converging onto two standards: USB4 and Thunderbolt 4. Both of these are set to debut by the end of the year in Intel’s upcoming Tiger Lake platform, and to set the scene Intel is updating us on the scope of its Thunderbolt 4 efforts.

Thunderbolt 4 is going to be a superset of TB3 and USB4, meaning that any Thunderbolt 4 Type-C host will be able to accept TB4, TB3, USB4, and USB 3/2/1 connections. Thunderbolt 4 will offer speeds up to 40 Gb/s, and there are a number of requirements for Thunderbolt 4 hosts and devices in order to be certified.

These requirements include:

  • Video, support 2x 4K or 1x 8K  (No detail at what refresh/bit-rate/chroma)
  • Data, PCIe at 32 Gbps (storage up to 3 GB/s)
  • Support for TB4 docks with four TB4 ports (one upstream, 3 downstream)
  • PC Charging on at least one port (for laptops up to 100 W)
  • Wake from sleep by peripherals connected to a TB4 dock
  • Requires Direct Memory Access protection (more on this later)


The first devices to come to market with TB4 support will be Intel’s Tiger Lake platform, for use in laptops, which will have TB4 baked right into the silicon. TB4 will be one of the base requirements for Intel’s Project Athena certification program, and Intel is set to release a new TB4 2m cable for most use cases. Intel is also working on optical 5-50 meter cables, which will also now support the TB4 multi-port accessory architecture, enabled by 4-port TB4 hubs.

There will be two host controllers, known as Maple Ridge JHL8540 and JHL8340, for use as host controllers in desktops, workstations, and laptops. We are told the package size and power requirements are essentially in-line with previous Titan Ridge TB3 controllers. The device controller, for use in docks, monitors, storage devices and such, is the Goshen Ridge JHL8440. All three of these controllers will be available by the end of the year.

Thunderbolt 4 has no costs associated with using it, the branding, or the logo, however there is a branding/logo license. Intel has opened up the TB4 standard, but as it stands is the only company that has publically announced its intention to make host and device controllers. The cables will be branded with the Thunderbolt Logo and a number 4, however ports on systems will only have the Thunderbolt Logo, making TB3 and TB4 use indistinguishable (we disagree with Intel that users don’t check what their system uses so using the same logo makes no difference to these users – we think the same argument can be used in order to showcase the logo on devices with the number 4).

Here’s a main slide showcasing the difference between all the different standards. Ultimately TB4 is backwards compatible with TB3 and USB4/3/2/1 standards.

One of the key focal points in our briefings with Intel is that Thunderbolt 4 will have an additional requirement this time round – Direct Memory Access protection to prevent physical attacks. In our briefing (and shown on the slide below), Intel initially stated that this requires Intel VT-d technology, which raised questions about Thunderbolt 4 being limited to Intel only systems.

The spokesperson later clarified that in order to gain certification, DMA protection is required, and Intel is using VT-d to do it. Intel refused to comment on how other vendors might implement DMA protection, stating that it would be up to them. While additional security protections are always a good thing, they ideally need to be based around open vettable standards, something which might limit Thunderbolt for another generation as an Intel-only technology (whereas USB is far more ubiquitous).

We’ve reached out to AMD late in the day, and they’ll be supplying a comment soon. I will update this post when I get something.

Update, AMD says the following:

The “Zen 2” architecture supports DMA security in pre-boot and OS environments via AMD-Vi (IOMMU) on USB and PCIe interfaces.

When asked specifically if AMD-Vi meets the requirements for TB4, AMD stated:

If the question is to do we support DMA? The answer is yes. Any questions about if this would satisfy another companies requirements for an interface they are developing would need to be directed at them.

When we asked Intel to confirm if AMD-Vi met the requirements for TB4's DMA protection, we were given the following quote:

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.

Overall, TB4 seems like a very capable standard, providing backwards compatibility, top class speeds, as well as new connectivity topologies. It will be interesting to see what the additional cost of adding TB4 onto various systems will be with Intel’s controllers, especially in the desktop space.

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  • Santoval - Friday, July 10, 2020 - link

    So Thunderbolt 4 is basically Thunderbolt 3+. Not a truly new version, just an optimization of the existing one, with some extras and better security. Maybe, just maybe, it should have been called either TB 3+ or TB 3.1 to point that out?
  • repoman27 - Saturday, July 11, 2020 - link

    One more time: Thunderbolt 4 fully supports USB4, uses it as the default signaling mode, and implements the Thunderbolt Alternate Mode to support backwards compatibility with Thunderbolt 3 and previous versions.

    Thunderbolt 3 does not support USB4 signaling at all. Therefore this is a fundamental change to the design and well worth incrementing the version number for. Maybe, just maybe, you're missing that point?
  • Santoval - Saturday, July 11, 2020 - link

    I am missing no point. Having Thunderbolt support USB4 (and previous), ensuring backwards compatibility and, er, simplifying(?) the huge cable mess/hole USB-IF dug themselves into, falls under the "some extras" & "optimization" category I mentioned above, and is in no way a "fundamental change" to the protocol. Besides, USB4 itself was based on TB3, even if the latter apparently does not support the signalling of the former, which is bizarre.

    When you trim, optimize, modify or extend an existing interconnect protocol (either internal or external) without upgrading it to higher speeds like what happened with *all* its previous versions it is not a truly new protocol by its *own* definition, not mine. TB4 is a modification, extension etc of TB3, not its actual successor, which is why it does not deserve a full new number revision.

    Just imagine PCI-SIG releasing PCIe 6.0 without doubling the speed over PCIe 5.0 but with adding a missing feature like full cache coherency and maybe making it compatible with CCIX and a couple of other interconnect protocols such as NVLink. Would this revision deserve a move to version 6.0 or would it more prudent to call it something like PCIe 5.1 (like they already do with minor revisions)? It's exactly the same with TB4.
  • repoman27 - Saturday, July 11, 2020 - link

    Except Thunderbolt 2 didn’t increase the signaling rate over the original version, it merely implemented channel bonding. Both are two channels at 10.3125 Gbit/s.

    So Intel’s choices were:

    1. Not support the new USB4 protocol and keep selling Thunderbolt 3 for the next few years until they can figure out how to deliver 40 Gbit/s PAM4 on a consumer I/O port.

    2. Support USB4 and Thunderbolt 3, which makes sense seeing as they have already integrated both into their CPUs and developed discrete controllers with similar capabilities including the first USB4 hub silicon, but simply bill it as “USB4 with Thunderbolt 3 Interoperability”.

    3. Support USB4 and Thunderbolt 3, set higher minimum performance targets and make certain aspects of those specifications normative rather than optional, develop a testing and certification program for hardware that also meets these stricter requirements, and refer to that as “Thunderbolt 4”
  • jabber - Saturday, July 11, 2020 - link

    Well managed to miss 1, 2 and 3 so far so maybe version 6?
  • KimGitz - Wednesday, July 15, 2020 - link

    Apple committed to continue supporting Thunderbolt and Intel baking it in their Tiger Lake, all I will really need to check when buying a computer is support for TB4.
    With a Thunderbolt 4 enabled computer I don't have to worry about whether the device is USB or Thunderbolt or what generation.
    One of the benefit of making Thunderbolt 4 also USB4 compliant is the new accessories architechure.
    Which makes me wonder if we can have a 4 port Dock connected to 4 Thunderbolt computers for 10G networking?
    If we look at the design wins for Ice Lake it is not difficult to imagine the kind of market presence TB4 will have once Tiger Lake comes out. I expect Microsoft will finally implement Thunderbolt on their next Tiger Lake powered Surface devices now that Intel has addressed security concerns.
    I was actually shocked to see Asrock with desktop motherboards supporting AMD Ryzen CPUs and Thunderbolt 3. Hopefully we will see more desktop motherboards supporting TB4.

    There is now a healthy selection of devices and accessories supporting TB3. Generally there is a performance increase between similar USB and Thunderbolt devices e.g storage, audio interfaces.

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