Intel unveiled Thunderbolt 4 on Wednesday, the next iteration of the I/O specification that provides a high-speed peripheral bus to docks, displays, external storage and eGPUs for PCs. Rather than increase the available bandwidth, however, Thunderbolt 4 provides more clarity and helps create new categories of products.
Thunderbolt 4 will debut later this year as part of Intel’s “Tiger Lake” CPU platform, as Intel originally announced during CES in January. We now know it will support 40Gbps throughput, but with tighter minimum specs. Thunderbolt 4 will guarantee that a pair of 4K displays will work with a Thunderbolt dock, and require Thunderbolt 4-equipped PCs to charge on at least one Thunderbolt port. Thunderbolt PCs will be able to connect to either “compact” or “full” docks with up to four Thunderbolt ports. Longer Thunderbolt cables will be possible, too.
One thing that doesn't seem to be changing is Thunderbolt's exclusivity. Intel developed Thunderbolt, and perhaps not coincidentally, OEM systems based on rival AMD’s CPUs have never had this technology. While AMD has officially dismissed the need for Thunderbolt, with generation 4 Intel appears to have made it even harder for AMD to get it, even if it wanted to.
What’s new in Thunderbolt 4?
Intel’s still pitching Thunderbolt as a single standard to rule them all, but the reality up to now has been complicated. You still have to squint hard at that USB-C-shaped port to determine which of the multitude of USB specifications it meets, including whether it’s a USB4 connection that happens to support Thunderbolt. To muddy things further, Thunderbolt also encompasses PCIe, DisplayPort, and USB Power Delivery standards.
Intel’s informal message is “just look for the Thunderbolt.” The small lightning-bolt icon means that port will support everything from USB 3.2 to USB4, and a high-speed Thunderbolt 4 cable will cover all of your bandwidth.
Though Thunderbolt 4 and USB4 share the same underlying protocol, Thunderbolt 4 includes more compatibility requirements than USB4 does. That makes Thunderbolt 4 the “complete version of USB-C,” according to Jason Ziller, the general manager for Client Connectivity for Intel, in a presentation to reporters.
Thunderbolt 4 also seeks to right some wrongs with its predecessor, Thunderbolt 3. For instance, Thunderbolt 3 was supposed to supply enough bandwidth to drive a pair of 4K displays at 60Hz or a single 8K monitor at 60Hz. “But not all of them do,” Ziller said of the current Thunderbolt 3 docks—because that spec’s loose minimum requirements allowed manufacturers to cut corners. Thunderbolt 4 promises to be rock-solid in that regard. In addition, the new spec will transfer at 32Gbps across PCIe (for storage speeds up to 3 gigabytes per second). It’s also fully USB4-compliant.
Laptops designed with Thunderbolt 4 will be required to offer input charging via a Thunderbolt 4 port, as an alternative to or replacement for proprietary “barrel” chargers (this is usually true with Thunderbolt 3 ports as well). Though Thunderbolt 3’s “Ice Lake” implementation allowed for Thunderbolt ports to be placed on either side of a laptop—a new feature for that platform—Intel’s not yet saying how Thunderbolt 4 ports will be arrayed within Tiger Lake laptops.
Intel’s also announcing that Thunderbolt cables, labeled with the lightning-bolt icon and a number ‘4,’ will be available in the standard 0.2m and 0.8m lengths, together with an additional 2-meter cable length that Ziller said should cost less than current 2-meter cables. There’s even a new optical Thunderbolt 4 cable design, with lengths ranging from 5 to 50 meters, that Ziller said he expects will be shipped sometime next year.
New Thunderbolt docks on the horizon
While Intel will supply its own Thunderbolt 4 solution as a selling point for Tiger Lake systems, it will also sell its own host silicon (“Maple Ridge,” specifically the JHL8540 and JHL8340 chips) as well as device silicon (“Goshen Ridge,” also known as the JHL8440). Thunderbolt 4 will also play a role in Intel’s ongoing Project Athena collaboration with PC vendors to develop premium thin-and-light notebooks.
Peripherals will evolve, too. We’re already seeing compact docks like Belkin’s Thunderbolt Dock Core, including some that are strictly bus-powered, in addition to larger, bulkier, more full-featured docks manufactured by Lenovo and others. Intel says the key feature for these new Thunderbolt 4 docks will be four Thunderbolt ports for connecting multiple devices, in either a tree structure, or by daisy-chaining them. Thunderbolt 4 host PCs will be backward-compatible with existing Thunderbolt 3 docks.
Thunderbolt ports have gradually gained ground. According to Ziller, hundreds of millions of PCs and PC accessories have shipped with Thunderbolt 3 silicon inside. Thunderbolt docks are rising, too: Intel projects 20-percent growth, versus the 10-percent annual growth of cheaper, slower USB-C hubs.
Displays have been slower to pick up the technology. Ziller suggested we’d see more with Thunderbolt 4, though he couldn’t say when or in what quantity.
Can AMD use Thunderbolt 4?
There’s one final wrinkle. One of the requirements for Thunderbolt 4 is that a laptop vendor must support what’s known as Intel VT-d based direct memory access (DMA), a security measure that protects the system by preventing direct memory access to preassigned domains. Because VT-d based direct memory access (DMA) is strictly an Intel technology, however, this requirement seemingly creates a barrier for AMD.
If nothing else, the rival chipmakers seem aligned in their desire to skirt the issue. “I wouldn’t read it as it’s only Intel, because of VT-d,” Ziller said. “If [at AMD] there was an equivalent technology that supports DMA protection, that supports prevention against physical attacks, then that would be the requirement.” Ziller deferred to AMD as to what that technology could be, and he also declined to say whether Intel would license the VT-d technology to competitors.
AMD’s position has been that its customers don’t want Thunderbolt. But the company has also said it believes it could supply Thunderbolt designs if it chose to. (The ASRock Phantom Gaming ITX TB3 motherboard combines Thunderbolt 3 with an AMD X570 chipset, allowing users, if not PC makers, to combine Thunderbolt and Ryzen themselves.)
“We do not find much demand from OEMs for Thunderbolt support,” an AMD representative said in an email when asked by PCWorld, before Intel’s announcement, why there had been few, if any, Ryzen-based notebooks with Thunderbolt in them to date. “There’s no technical reason preventing AMD from supporting Thunderbolt. A discrete Thunderbolt chipset can connect to the CPU via PCI [Express].”