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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  • serendip - Thursday, July 9, 2020 - link

    So TBT3 is a superset over USB, just like DisplayPort Alt Mode? The device is supposed to follow USB4 for full compatibility and add alternate modes if needed. Reply
  • Spunjji - Wednesday, July 8, 2020 - link

    Is it just me or is Thunderbolt 4 looking increasingly like a rehash of Thunderbolt 3, just guaranteed to work at full speed and with some deeper vendor lock-ins?

    The "one port to rule them all" concept could be beautiful, but as it is, it's actually just adding to the confusion because it's impossible to differentiate from Thunderbolt 3 and will probably not be ubiquitous.
    Reply
  • DigitalFreak - Wednesday, July 8, 2020 - link

    It's TB3 with a 1m longer cable and optional stuff now required. At least USB increases it's speed with every version. Reply
  • chaos215bar2 - Wednesday, July 8, 2020 - link

    There are plenty of 2m TB3 cables which support 40Gb/s data and 100W charging. What's different, if I'm reading correctly, is that Thunderbolt 4 cables must support full backwards compatibility. That could just be a change to the active hardware used on 2m cables.

    What's less clear is whether the longer optical cables will be fully compatible. Based on what's said here, I'd expect a 50m Thunderbolt 4 cable to also work as a really expensive USB 2.0 cable.
    Reply
  • DigitalFreak - Thursday, July 9, 2020 - link

    I just saw that there are 2m TB3 active cables now that can do the full 40Gbps. The last time I looked into it you could still only do a max of .5 (or 1?) meters @ 40Gbps. Those active cables are expensive af though. Don't even get me started on the fiber ones. Reply
  • repoman27 - Wednesday, July 8, 2020 - link

    Thunderbolt 4 is USB4 with full support for the Thunderbolt 3 and DisplayPort Alternate Modes. This is significant in that Thunderbolt 3 controllers do not support USB4 at all. The two protocols are not the same.

    The differences between USB4 and TBT3 are discussed starting at page 68 in this slide deck: https://www.usb.org/sites/default/files/D2T1-3%20-...
    Reply
  • PaulHoule - Wednesday, July 8, 2020 - link

    Whoever made that "How Thunderbolt 4 is different from other solutions?" slide should make luxury car commercials.

    My concern is this: I have used Mac and Dell computers with Thunderbolt support and I'd say the experience is good on the mac and worse on Windows. A newer Dell I use came with a Thunderbolt dock that "just works" (charging, display, network and HID) but I have had a hard time finding pairs of machines and docks that work completely. Often everything works except the network. My Alienware (also Dell) did OK with a Thunderbolt monitor I tried, although it took much longer to configure itself than macs did.

    So now I have a "four plug" docking solution at home which works with every laptop I have tried, which involved trying quite a few different devices, giving up on Logitech/Plantronics dongles for Bluetooth, ... It supplies 250W, but it does not have the one-plug simplicity that i wish for.
    Reply
  • schizoide - Wednesday, July 8, 2020 - link

    Originally TB4 was rumored to be 4 lanes of PCIe 4.0, which would double the bandwidth. That extra bandwidth would have been very useful for eGPU purposes, particularly if you want to use your laptop's integrated display. Pity it turned out to be such a minor update. Reply
  • npz - Wednesday, July 8, 2020 - link

    It's good that they're *finally* addressing the DMA security hole in TB. I've warned people about it online since the beginning and its spiritual predecessor, Firewire also suffered from it. It's the same with external accessible PCIE btw. (but that's virtual non-issue since only enteprise machines have external hotplug pcie)

    But ironically also since the beginning, using IOMMU aka Vt-d has always been the solution! IOMMU isn't just for virtualization, it's to protect from roque and badly behaving devices/firmware by assigning virtual address space to every device or virtual function.
    Reply
  • Techtree101 - Wednesday, July 8, 2020 - link

    Correction: It will offer up to 80 Gb/s when in a single direction. 40 GB/s is for bi-directional use. So, for example, DisplayPort 2.0 will be using it at 80 Gb/s. Reply

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