Intel recently updated its lineup of desktop processors with the release of the 14th Gen Core "Raptor Lake Refresh" processors. However, it was mistakenly reported that these processors support the upcoming Thunderbolt 5 connectivity standard. Intel reached out to clarify that the 14th Gen Core desktop processors do not actually support Thunderbolt 5, despite Intel having their own TB5 controller design called "Barlow Ridge." The Barlow Ridge controllers are not expected to be available until Q1 2024, and the currently shipping "Maple Ridge" controllers only support Thunderbolt 4. Even when Barlow Ridge becomes available, it will not be compatible with the Raptor Lake Refresh socketed desktop processors.
In September, Intel announced the Thunderbolt 5 standard alongside the technical details of its upcoming Core "Meteor Lake" mobile processors. Thunderbolt 5 offers a doubling of bandwidth to 80 Gbps per direction, thanks to a new feature called Bandwidth Boost. With Bandwidth Boost enabled, users can achieve 120 Gbps of bandwidth in one direction and 40 Gbps in the opposite direction. This feature is particularly useful when transferring large data sets from a Thunderbolt 5-based external storage device to a local machine. The receiving bandwidth is boosted to 120 Gbps, while the transmission bandwidth is reduced to 40 Gbps. The roles are reversed when exporting data to the external storage device.
It's important to note that Thunderbolt is a complex bus that combines various links, including PCIe and DisplayPort, to achieve its advertised bandwidth. The default per-direction bandwidth of Thunderbolt 5 is 80 Gbps, which is derived from the underlying PCIe bandwidth of PCIe Gen 4 x4 (64 Gbps). Similarly, the advertised 120 Gbps bandwidth of Thunderbolt 5 is actually 96 Gbps, and the current Thunderbolt 4's 40 Gbps per direction is equivalent to 32 Gbps PCIe bandwidth.
Thunderbolt and USB4 are PCIe-based serial interconnect standards that utilize Rx and Tx lanes. To achieve 120 Gbps through a PCI-Express 4.0 x4 connection between the Barlow Ridge controller and the processor's PCIe root complex, the root complex must be able to re-task sub-lanes of two PCIe lanes for either purely-Tx or purely-Rx. This requires awareness at the end of the PCIe root complex. The Bandwidth Boost feature is illustrated in an Intel slide, where three out of four links are loaded toward one direction to achieve 120 Gbps, while the remaining link is in the opposite direction.
Intel has stated that when Barlow Ridge is released in Q1 2024, it will have compatible processors at launch, although the specific processors have not been disclosed. It is possible that Intel is updating its mobile processor lineup to support Thunderbolt 5, including the Bandwidth Boost feature. Intel has already provided technical details about its upcoming Core "Meteor Lake" mobile processors, but no product launch dates have been mentioned. The 2024 International CES in January could be a potential event for Intel to unveil new processors.
For users on the 14th Gen Core socketed desktop platform, Thunderbolt 4 is available using motherboards or add-on cards with Intel's "Maple Ridge" controller. Thunderbolt 5 and AI Boost will only be available on socketed desktop platforms with Intel's next-generation processors. "Meteor Lake" will not be compatible with socketed desktop platforms, leaving "Arrow Lake-S" as the likely candidate for Thunderbolt 5 support in the second half of 2024.
