Let’s get this out of the way up front: Intel’s new Thunderbolt 4 connection isn't technically faster than Thunderbolt 3, at least when it comes to overall throughput. (They both offer up to 40 gigabit per second speeds.) But the company is justifying the new version number other ways: Namely, by cranking up the minimum requirements for systems with the new connection.
Thunderbolt 4 PCs will be able to connect to at least two 4K displays, whereas the previous requirement was just one. Additionally, the new connection supports PCIe data speeds up to 32 Gb/s, twice as fast as before. So you can expect to see incredibly fast Thunderbolt 4 external drives eventually. And you can be rest assured that at least one of your Thunderbolt 4 ports will support laptop charging, which is a bit of a hit-or-miss capability with current systems.
All of these new baseline features gives Intel another premium offering to add on top of the upcoming USB 4 standard, which, confusingly enough, basically does everything Thunderbolt 3 did. (It’s baffling why Intel didn’t open up the licensing for that connection earlier.) Thunderbolt 4 will also fully support USB 4 — it has to, since they both use the USB-C cable standard — as well as docks that include up to four additional Thunderbolt 4 ports.
Crucially, Intel says the new connection will also require protection against direct memory attacks (DMA) like the recent “Thunderspy” vulnerability. That attack could theoretically allow a hacker to steal data from your device, even if your PC was locked and had encrypted storage. Those DMA protections rely on Intel’s Virtualization Technology for Directed I/O (VT-d), which was supported on Thunderbolt 3 PCs, but was only strongly recommended for computer makers to follow. Now it’s an essential feature. VT-d creates an isolated memory region for devices, which prevents them from reading and writing to other locations.
It's still surprising that Intel didn't require significant Thunderbolt DMA protection until now, especially given the potential for data theft from such a fast interface. But the new requirement in Thunderbolt 4 might make some PC makers like Microsoft, which has avoided the connection over security risks, take a second look. (I'm still waiting for a Thunderbolt-equipped Surface device that could run an external GPU.)
Intel says it plans to ship Thunderbolt 4 controllers to manufacturers later this year, and you can expect to see it on Project Athena notebooks around the same time.